HYDRAULIC LESSONS
A Project-Based Approach to Fluid Mechanics and Hydraulics in Civil Engineering
1 January 2024
Hydraulic Lessons by Kenneth Lamb is licensed under CC BY-NC-SA 4.0. To view a copy of this license,
visit https://creativecommons.org/licenses/by-nc-sa/4.0
Hydraulic Lessons
Table of Contents
LESSON 1: WATER DEMAND, HYDROSTATICS............................................................................................... 2
LESSON 2: PIPELINE DESIGN & ANALYSIS.................................................................................................... 10
LESSON 3: WATER DISTRIBUTION NETWORK ............................................................................................. 22
LESSON 4: SELECTING A CENTRIFUGAL PUMP ............................................................................................ 32
LESSON 5: FLOOD DIVERSION ..................................................................................................................... 45
LESSON 6: OPEN CHANNEL MODELING ...................................................................................................... 56
REFERENCES ................................................................................................................................................ 61
APPENDIX A – Water System Development Guidelines ........................................................................... A-1
APPENDIX B – Hydraulic Reference Tables ................................................................................................B-1
1
Hydraulic Lessons
Lesson 1: Water Demand & Hydrostatics
LESSON 1: WATER DEMAND, HYDROSTATICS
Project Background
A water distribution system consists of several components such as a water source (lake, reservoir, river,
groundwater well, even the ocean in some cases), a storage facility (a reservoir or tank), and distribution
system (including piped distribution as well as canals or natural rivers). Water distribution systems not
only transport water but they also transport energy. This means that water system is also tasked with
managing the energy in the system.
You learned in science class long ago that there are two forms of energy: potential and kinetic. Many
water systems in the world are powered by potential energy because the water source happens to be at
a higher elevation than the end user. Think of the City of Rome. Rome is located at the confluence of
the Tiber and Aniene rivers yet when ancient Romans supplied water to their city, they tapped the
source at higher elevations then built aqueducts to transport the water to the city.
As you progress through this first lesson on fluid mechanics and hydraulics you will consider the specific
case of Chagüite – a community in Nicaragua, east of Totalgalpa that needs to size and locate a tank to
be used to store water for their community. The community comprises of about 250 residents living in
50 homes. The hilly topography will be a challenge. As the engineer on the job, you need to estimate
the size of the tank, identify the tank location, and then compute the static pressure head at each home.
If these words are meaningless to you, then pay attention to the lesson and listen to each video
completely.
Lesson Overview
In order to complete this project, you will need to learn about water demand, fluid properties, statics,
and buoyancy. This lesson is divided into four (4) tasks: Water Demand, Fluid Statics, Hydrostatic Forces,
and Buoyancy. Each task covers a specific topic (similar to what you would receive in one or two
lectures) and includes practice problems to assess your progress. Read through the lesson and complete
each activity (reading, watching videos, and lesson practice). Complete each task in the order they are
provided.
Learning Outcomes
At the end of this module you will be able to:
•
•
•
•
•
•
Describe the different types of water demand scenarios: Average Day, Maximum Day and
Peak Hour (or Max Hour)
Determine the static head of a system
Define fluid density, unit weight, and specific gravity
Compute the hydrostatic pressure of a fluid on a rigid body.
Determine the static head of a given water supply on a water system
Compute the buoyancy force exerted on a submerged object
2
Hydraulic Lessons
Lesson 1: Water Demand & Hydrostatics
Task 1.1 – Water Demand
How much water we use is not a constant. It varies, as you can imagine, throughout the year as well as
throughout the day. Even if you are not a water manager, it is not stretch of the imagination that most
people use more water during the summer and less in the winter. Also, I’m sure you can imagine that
your personal demand varies throughout the day as you use less water at night, but more water in the
morning or in the evening.
This variation creates a challenge for water managers. In order to classify the operating scenarios for a
water system, water managers have come up with several new terms you need to understand: Average
Day, Maximum Day and Peak Hour demand scenarios. Video 1-1 Water Demand, introduces you to
these concepts and provides you with the introduction to estimating the water demand for a given
water system.
Task 1.2 – Fluid Statics
Here, you will learn how to compute the pressure exerted by a fluid on a distribution system. This
concept provides the conceptual foundation for how we plan and design water distribution systems. We
are using the videos from ME Online as well as other videos from Kenneth Lamb on YouTube.
Pressure
Pressure is measure of a force applied to a unit area and is
typically expressed in kilopascals (kPa) or pounds (force) per
square inch (psi). While pressure is a common term, for
fluids it is important the contrast between gauge and
absolute pressure. Gauge pressure is what can be observed
from a pressure gauge. The pressure gauge exists in an
environment and therefore it, as well as the fluid it is
measuring, are also being acted upon by the ambient
pressure. We assume that the ambient pressure is
atmospheric pressure in most cases. This means that
absolute pressure includes gauge pressure and atmospheric
pressure.
For further explanation, please review Video 1-3 Pressure.
Hydrostatic Pressure
Density
The density of a fluid, ρ, is simply its
mass divided by its volume.
ρ=M/V
The density of an object is not a
function of gravity. If we wish to
include gravity then we multiply the
density by gravitational constant to
obtain the unit weight, γ which has
units of N/m3 or lb/ft3.
γ=ρ∙g
Finally, since the properties of water
are so well known we often talk about
other fluids as relative to the density
of water by computing its specific
gravity.
Video 1-2 Density, provides a more
detailed explanation of these three
concepts.
Pascal’s law states that, for a point within a fluid, the
pressures acting on the point in each direction (from the x,
y, or z direction) are equal. This means that pressure is
isotropic, meaning that it is independent of direction.
Therefore Pressure is a scalar and not a vector. Video 1-4 Pascal’s Law provides the proof of this
concept.
For Hydrostatic pressure there are two more principles that you should learn:
1. The hydrostatic pressure in an incompressible fluid increases as the depth of the observation
point increases within the fluid. The pressure does not change if it moves laterally in the fluid.
3
Hydraulic Lessons
Lesson 1: Water Demand & Hydrostatics
This principle is summarized through Equation 1-1.
𝑃 = 𝛾ℎ
Eq 1-1
The units of P are N/m2 for SI and lbf/ft2 using American Standard. In Equation 2-1, γ is the unit weight
of the fluid and h is the height of the water column above the observation point. ‘Water Column’ is an
important concept because many fluid books only refer to a point in some arbitrary basin. Therefore,
you are left visualizing the pressure at a point some distance h beneath the surface of the water. Video
1-5 Hydrostatic Pressure Gradient provides the mathematical proof of this concept in general and Video
1-6 Hydrostatic Pressure Distribution provides the proof of Eq. 1-1.
Hydrostatic Pressure Applied
As mentioned in the task overview, these concepts are the foundation for designing water systems. The
earliest water systems ever made by humankind utilized potential energy to distribute the fluid to the
user. Merging the concepts of hydrostatic pressure and potential energy, we see that the pressure in a
system is a function of the elevation difference (or h) between the storage tank and the outlet of the
system. While pressure is a value measured in units of kilopascals or pounds per square inch, we have a
new term pressure head which has units of meters or feet.
In other words, a common scenario in water system planning is to ensure that the system does not have
too much or too little pressure. Since the thresholds of ‘too much’ and ‘too little’ are both set by the
water agency, and because the unit weight of the water is known, we are often solving Eq 1-1 for h, to
find the height, h, a tank needs to be above system.
Video 1-7 Static Head shows how the concepts of pressure and potential energy come together in a
rather helpful unit conversion (between lb/in2 and feet):
1 kPa = 1 kN/m2 = 0.102 m of pressure head
assumes γ = 9.798 kN/m3 the unit weight of water at T = 15˚ C
1 lbf/in2 of pressure = 2.309 feet of pressure head
assumes γ = 62.37 lbf/ft3, the unit weight of water at T = 60˚ F
Task 1.3 – Hydrostatic Forces
The force created by hydrostatic pressure is calculated in Eq. 1-2.
𝐹 = 𝑃𝐴
Eq 1-2
Where A is the area of the object experiencing the force.
When computing the Force using Equation 2-2 use the
pressure that is present at the centroid of the object
receiving the force. If you are considering the force on the
wall of a square tank, then the pressure is evaluated at the
centroid of one of the walls (i.e. h/2). If you are interested in
knowing the force applied to a gate (to an opening in the tank
wall), then the force will be evaluated at the centroid of the
gate (i.e. h – hgate/2).
4
Hydraulic Lessons
Lesson 1: Water Demand & Hydrostatics
This formula is derived in Video 1-8 Hydrostatic Force on a Plane Surface.
Example 1-1: The tank has a wall that is 20 feet wide and the gate is 4 feet wide. If h = 10 feet and hgate =
4 feet, what is the resulting force acting on the (a) wall and (b) the gate. Assume the fluid is water at
100˚ F.
(a) Look up the unit weight of water at 100˚ F = 62.0 lbf/ft3. Compute the Area of the wall, Awall =
200 ft2.
ℎ
𝑙𝑏𝑓 10 𝑓𝑡
𝑙𝑏𝑓
= 62.0 3 ∙ (
) = 310 2 (𝑜𝑟 𝑗𝑢𝑠𝑡 "𝑝𝑠𝑓")
2
𝑓𝑡
2
𝑓𝑡
𝑙𝑏𝑓
𝐹𝑤𝑎𝑙𝑙 = 𝑃𝑤𝑎𝑙𝑙 𝐴𝑤𝑎𝑙𝑙 = 310 2 ∙ 200𝑓𝑡 2 = 𝟔𝟐, 𝟎𝟎𝟎 𝒍𝒃𝒇
𝑓𝑡
𝑃𝑤𝑎𝑙𝑙 = 𝛾
(b) For the Gate:
𝐴𝑔𝑎𝑡𝑒 = 4 𝑓𝑡 ∙ 4 𝑓𝑡 = 16 𝑓𝑡 2
1
𝑙𝑏𝑓
1
𝑙𝑏𝑓
𝑃𝑔𝑎𝑡𝑒 = 𝛾(ℎ − ℎ𝑔𝑎𝑡𝑒 ) = 62.0 3 ∙ (10𝑓𝑡 − ∙ 4 𝑓𝑡) = 496 2
2
𝑓𝑡
2
𝑓𝑡
𝐹𝑔𝑎𝑡𝑒 = 𝑃𝑔𝑎𝑡𝑒 𝐴𝑔𝑎𝑡𝑒 = 496
𝑙𝑏𝑓
∙ 16 𝑓𝑡 2 = 𝟕, 𝟗𝟑𝟔 𝒍𝒃𝒇
𝑓𝑡 2
Since force is a vector, the location and direction matter. Therefore, knowing how the force acts on a
plane is important to analyzing the resulting force on the walls of a tank or on a gate opening inside the
tank. As depth increases the pressure increases linearly. If you sketch this relationship, you would
sketch a triangular shape. The resulting force acts through the centroid of the ‘distribution triangle’, or
about 2/3rd of the distance down along the triangle.
Statics Review: When considering the entire wall, the force acts at a depth of 2/3 h, down from the
surface of the water. When considering the pressure distribution is a trapezoid shape. The centroid of
the trapezoid is found at
ℎ𝑔𝑎𝑡𝑒 3ℎ−2ℎ𝑔𝑎𝑡𝑒
( 2ℎ−ℎ
3
ℎ
𝑔𝑎𝑡𝑒
) from the bottom of the gate. Relative to the water surface,
3ℎ−2ℎ
this can be expressed as ℎ − 𝑔𝑎𝑡𝑒
( 2ℎ−ℎ 𝑔𝑎𝑡𝑒 ).
3
𝑔𝑎𝑡𝑒
Video 1-9 Center of Pressure on a Plane Surface provides a detailed overview of locating a force on a
plane.
Example 1-2: If h = 12 feet and hgate = 3 ft, find the location of the resulting force relative to the water
surface on the wall and the gate.
Resulting force on wall:
2
( ) ∙ 12𝑓𝑡 = 8 𝑓𝑡
3
Resulting force on the gate:
5
Hydraulic Lessons
ℎ−
Lesson 1: Water Demand & Hydrostatics
ℎ𝑔𝑎𝑡𝑒 3ℎ − 2ℎ𝑔𝑎𝑡𝑒
3 3(12) − 2(3)
36 − 6
30
= 12 −
= 10.57
(
) = 12 − (
) = 12 −
3
2ℎ − ℎ𝑔𝑎𝑡𝑒
3 2(12) − 3
24 − 3
21
This information is needed to compute the impact of the force on the wall or gate to determine if the
wall will deflect, or how much force is needed to open the gate and release the fluid. To fully compute
deflection, we would need information about the material used to construct the tank wall
Example 1-3: A sluice gate is a common type of water gate which slides up and down to open and close
an opening in a wall. The sluice gate is made of steel and sits in a steel railing, but the edges of the gate
that touch the railing are coated in rubber (Friction Factor between rubber and steel connection, μ =
0.40). Use the results from Example 2-1(b) to compute the force needed to lift the sluice gate in its
tracks (i.e. overcome the friction force).
𝐹𝑟𝑖𝑐𝑡𝑖𝑜𝑛 𝐹𝑜𝑟𝑐𝑒: 𝐹𝐹 = 𝜇𝐹𝑁 = 0.40 ∙ 8,590 𝑙𝑏𝑓 = 𝟑, 𝟒𝟒𝟎 𝒍𝒃𝒇 𝒂𝒄𝒕𝒊𝒏𝒈 𝒅𝒐𝒘𝒏𝒘𝒂𝒓𝒅
Task 1.4 – Buoyancy Force
Buoyancy is most often associated with boats or some other object we want to see float in a liquid. The
buoyancy force applied to an object in a fluid comes from the displaced fluid as it pushes back on the
object. The effect exerts a force on the object suspended in a fluid. The buoyancy force is computed
using the following formula:
𝐹 = 𝑉𝛾
Eq 1-3
F represents the resulting buoyancy force, V is the volume of the fluid displaced by the object, and γ
represents the unit weight of the fluid. This is knowns as Archimedes’ principle and is derived in Video
1-10 Buoyancy & Archimedes Principle.
To the Civil Engineer, the buoyancy creates problems that we often need to overcome, rather than an
opportunity that we can exploit. This is because much of our built infrastructure lies beneath the
ground surface – our pipe to bring us water, or to carry away our sewage and storm water is all
underground. Many buildings and other structures have foundations that lie beneath the ground
surface. Anything we place beneath the ground can be impacted by buoyancy forces depending upon
the level of the ground water table.
Video 1-11 Buoyancy Applied to a couple of situations encountered in Civil Engineering Contexts. You
should know what a distributed load is before watching this video.
6
Hydraulic Lessons
Lesson 1: Water Demand & Hydrostatics
Lesson 1 Practice
1. Draw a schematic of a water system include on the schematic a source for the water, a source of
energy, the user, and the piping to connect everything.
2. Both Tucson, Arizona, USA and Filadelfia, Boqueron, Paraguay are hot, arid regions of the world.
Why might the water demand be different in each location?
3. Water is the Maximum day demand for a community that has 200 homes. Assume a water
demand of 250 gal/day/capita and an average of 3.2 capita/housing unit.
4. A reservoir of water has an outlet gate that is 3.5 feet tall
and installed at the bottom of the tank. Compute the
hydrostatic pressure at Point 1, 2, and 3 shown on the
Figure. Assume the fluid is:
a. Water at 60˚ F.
i. 2.82
b. California Crude Oil (SG = 0.918)
i. 0 psi
c. Chlorine (SG = 1.42)
15 psi
5. Compute the resulting force of the water exerted on the
foundation of the tank (the force acting downward on the bottom of the tank). The tank has a
diameter of 30-feet.
440,750
6. The opening of the tank is a square sluice gate (3.5 ft x 3.5 ft).
a. Compute the hydrostatic force on the sluice gate assuming it contains water at 60˚ F.
6,302
b. Where is the hydrostatic force located? Give your answer as an elevation.
E
7. Complete the following tasks using the information provided by Figure 1-1.
a. If Lake 1 is used as the City water supply, what is the minimum and maximum static
head supplied by the Lake (assuming a pipe connected the lake directly to the city water
system. NOTE: The minimum static pressure will be at the highest elevation of the city
and the maximum static pressure will be observed at the lowest elevation.
b. If you wanted to use the rivers as the water supply, what is the minimum elevation
along the river where you could start an aqueduct if you needed a minimum of 30 psi
static pressure at the city?
7
Hydraulic Lessons
EL = 490’
Lesson 1: Water Demand & Hydrostatics
EL = 493’
500’
EL = 487’
500’
600’
500’
400’
300’
200’
400’
100’
300’
Figure 1-1. Plan view of city with potential water supply from two rivers and three lakes.
8. A new waterline has a large valve that will be installed inside a vault. The vault has dimensions
of 8 feet wide, 12 feet long, and 7.5 feet tall (as measured from the outside of the concrete
structure). What is the buoyancy force acting on the vault if it is installed below the
groundwater level?
9. An 18-inch PVC SDR 35 sanitary sewer line is to be installed. The installation will be completely
below the groundwater level. What is the buoyancy force acting on the pipeline in terms of a
force per linear foot?
8
Hydraulic Lessons
Lesson 1: Water Demand & Hydrostatics
Lesson 1 Project
A community in Nicaragua needs to size and locate a tank to be used to store potable water. The goal
will be to create a water distribution system, but for now we will focus on the storage tank. The
community itself is stretched along a ridge line in the northern Nicaraguan municipality of Totogalpa,
Madriz (Please see attached .kmz file). The community comprises of about 250 residents in 56 homes.
Project Tasks
To complete this project, you need to determine the size of the tank and you need to locate it within the
community so that it provides sufficient pressure to each home. This Google Earth file shows the
location of the community and some of the local infrastructures including the homes, the main road,
and the existing well.
1. Draw a schematic for their system. Include the well, tank and a simplified representation of the
homes within the community. Label the elevations for each object in the schematic.
2. How much water does a person need? Research this answer on the internet and cite your
sources. Provide an estimate that you think is appropriate for Northern Nicaragua. This means
your research may tell you that the typical water demand is X L/day, but given our specific
location, you may adjust this value to Y L/day. Provide a justification for the number that you
choose.
3. How much water storage is appropriate? Decide if the average day or maximum day demand is
the right scenario to determine the size of the tank and then compute the volume of the tank.
4. Where should the tank be located (location and elevation)? Using Google Earth, place a pin in a
spot where you think the tank should go. Write the assumptions and the considerations that
you made to decide that location. Estimate the minimum tank height based upon your choice of
minimum static pressure for the community.
5. How much static pressure is at each home within the community? Given the height of the tank,
provide the static pressure for the homes at the highest elevation and the lowest elevation
within the community.
Submission
Provide a written summary of your work, including a brief background of the tasks that you completed.
Provide a description of your analysis to determine the water demand, the size of the tank, the tank
location, and the range of static pressures within the community. Include a map of the community
showing the location of your tank and the houses with the lowest and highest static pressures within the
community. This map should also have a north arrow, and a title block containing a figure number,
description, and project name.
Google Earth File
9
Hydraulic Lessons
LESSON 2: PIPELINE DESIGN & ANALYSIS
Project Background
A frequent scenario faced by water resource engineers is providing water to new housing. A developer
with some land can make more money if they subdivide the parcel into individual housing lots and sell it
off in pieces (the sum of the individual parts is greater than the whole). Of course, that is only true if the
neighborhood has water.
There is a new development that is being built relatively close to an existing water system. To provide
water to the new homes a waterline needs to be installed so that the new homes are connected to the
existing water distribution system. As the engineer on the job, you will design the water system (draw it
technically) and then analyze the pipeline to ensure it complies with the owner’s (the water agency’s)
performance guidelines.
Lesson 2 Overview
This module is divided into three (3) tasks: Velocity Criteria, Headloss Methods, and Residual Pressure.
Each task covers a specific topic (similar to what you would receive in one or two lectures) and includes
practice problems to assess your progress. Read through each learning task and complete each activity
(reading, watching videos, and lesson practice). Complete each task in the order provided.
Learning Outcomes
At the end of this module you will be able to:
•
•
•
•
•
•
•
Design a pipeline to connect a source to a user
Select the pipeline material
Select pipeline appurtenances (bends, valves)
Describe viscosity of a fluid
Analyze the average velocity within a pipeline
Analyze the unit headloss and total headloss of a pipeline
Analyze the residual pressure at a point in a pipeline.
10
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
Task 2.1 Velocity Criteria
Conservation of Mass
While Greek philosophers knew that nothing comes from nothing it took a while before scientists
defined that mass cannot be created nor destroyed. In a closed system (for example, a pressurized pipe
that does not leak) the mass of fluid entering the pipe is the same as what exists the pipe. Video 2-1
derives the equation for conservation of mass. Pay special attention to the incompressible, steady flow
relationships.
In practice, conservation of mass becomes a tool we use to size pipelines. Most water agencies state a
maximum pipeline velocity for two reasons: (1) manage the amount of friction loss, (2) decrease the risk
of damaged caused by hydraulic transients (e.g. water hammer).
Water agencies specify various maximum velocity values. For instance, the Las Vegas Valley Water
District (Las Vegas, NV) uses 8 ft/s as the maximum velocity in their system. Western Municipal Water
District (Riverside, CA) specifies a maximum of 7.5 ft/s. Be aware of the guidelines in your system.
Video 2-1 Maximum Velocity Criteria shows how to apply conservation of mass to size a pipeline given a
maximum velocity criterion and a known water demand. After completing Unit 2.1 you should be able
to complete Project 2, Task 3a.
Task 2.2 Headloss Methods
In this task, you are introduced to three methods of calculating the headloss due to friction.
1. Darcy-Weisbach
2. Hazen-Williams
3. Manning
Video 2-2 – Headloss Methods introduces you to each of these methods. Table 1 provides various
forms of all three equation for both SI and US Customary units. Table 2 shows each equation solved for
unit headloss. The boxed forms below are the most common among the videos.
Table 2-1. Various forms of the most common used headloss equations
Units
Darcy-Weisbach
Common Form:
𝑓 𝐿 𝑉2
𝐷 2𝑔
𝑣 = 𝑘𝐻 𝐶 𝑅 0.63 𝑆𝑓0.5
𝑓 8 𝐿 𝑄2
ℎ𝐿 =
𝑔 𝜋 2 𝐷5
3.58 𝑄 1.85
ℎ𝐿 = 𝐿 (
)
𝐶 𝐷 2.63
𝑓 8 𝐿 𝑄2
𝑔 𝜋 2 𝐷5
2.31 𝑄 1.85
ℎ𝐿 = 𝐿 (
)
𝐶 𝐷 2.63
𝑓 𝐿 𝑄2
ℎ𝐿 =
𝑔 𝐷5
3.55 𝑄 1.85
ℎ𝐿 = 𝐿 (
)
𝐶 𝐷 2.63
ℎ𝐿 =
Q (m3/s),
D (m),
L (m)
Q (ft3/s),
D (ft),
L (ft)
Q (gal/min),
D(in),
L (ft)
Hazen-Williams
ℎ𝐿 =
Manning
𝑣=
𝑘𝑚 2⁄ 1⁄2
𝑅 3 𝑆𝑓
𝑛
ℎ𝐿 = 𝐿 (
ℎ𝐿 = 𝐿 (
ℎ𝐿 = 𝐿 (
3.21 𝑄 𝑛
8
𝐷 ⁄3
2
)
1.45 𝑄 𝑛
8
𝐷 ⁄3
2
)
𝑄𝑛
8
11.3 𝐷 ⁄3
2
)
11
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
Table 2-2. Various forms of the headloss equations solved for unit headloss.
Units
Q (m3/s),
D (m),
L (m)
Q (gal/min),
D(in),
L (ft)
Darcy-Weisbach
Hazen-Williams
82.7𝑓𝑄 2
ℎ𝐿 =
𝐷5
150 𝑄 1.85
)
ℎ𝐿 = (
𝐶 𝐷2.63
31.1𝑓𝑄 2
ℎ𝐿 =
𝐷5
148 𝑄 1.85
)
ℎ𝐿 = (
𝐶 𝐷2.63
Manning
ℎ𝐿 = (
ℎ𝐿 = (
134 𝑄 𝑛
8
𝐷 ⁄3
2
)
2.80 𝑄 𝑛
8
𝐷 ⁄3
2
)
Reynolds Number
The Reynolds number is a dimensionless parameter that seeks to quantify the state of the flow. We use
the the Reynolds number to classify a flow as laminar and turbulent.
•
•
•
Laminar flow - when fluid particles travel in relatively straight lines within the fluid. Like small
cars on a highway all travelling in their lanes. Fluids flowing a low velocities or highly viscous
fluids tend to have laminar flow characteristics. Laminar flow follows Newton’s laws of motion,
so you may see it referred to as Newtonian flow.
Turbulent flow – when all fluid particles do not flow straight but swirling and mixing paths.
Every car is driving any direction it pleases bumping into other cars along the way. An equation
to model turbulent flow remains one of the nine unsolved mathematical problems.
Mixed flow – the flow between lamina r and fully turbulent is often mized which some flow lines
following straight paths while others do not. For the most part, in water systems, sewer
systems, and flood control systems, we observe mixed flow.
The Reynolds number is computed using Eq. 2.1:
𝑣𝐷
𝑅𝑒 = 𝜈
In this equation v is the average velocity of the fluid flowing along a conduit of diameter D. The Greek
letter, ν , represents the kinematic viscosity of the fluid.
Viscosity
Viscosity is the resistance of a fluid to a shearing force. When water flows in a pipeline the velocity
of the fluid along the center of the pipe moves at a faster velocity than at the walls because the fluids
is experiencing a shearing force. A fluid with higher viscosity will resist the shearing force decreasing
the velocity difference between a particle in the center of the channel and the walls.
Viscosity has unit of N∙s/m2, or lbf∙s/ft2. Video 2-3 Viscosity explains this concept in more detail.
It should be noted that what Video 1-1 describes is the absolute (or ‘dynamic’) viscosity, μ. If we
divide the dynamic viscosity by its density, then we obtain the kinematic viscosity, ν, of the fluid.
Kinematic viscosity has units of m2/s or ft2/s. Kinematic viscosity does not consider the force applied
to the fluid to create the shearing stress.
12
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
The relative roughness of the pipeline is the equivalent sand roughness, ks, divided by the diameter of
the conduit. Some texts refer to this quantity simply as ε/D, where ε represents the absolute or sand
roughness.
The best tool for estimating the friction factor is the Colebrook-White equation (Eq 2-2).
1
√𝑓
= −2𝑙𝑜𝑔10 (
𝜀 ⁄𝐷
2.51
+
)
3.7 𝑅𝑒√𝑓
f – Friction Factor;
ε – Equivalent Sand Roughness (m, ft/in)
D – Internal, Nominal Pipe Diameter (m, ft/in)
Re – Reynolds Number
NOTE: When using this equation ensure that the units of ε and D are the same.
To solve for the friction factor, you must guess the starting friction factor, f, then compute the left and
right-sides of the equation. If they are not equal, vary the friction factor until both are equal. This
process is tedious by hand, so a spreadsheet can run the iterations (in other words the guesses)
automatically. For even faster results use the Goal Seek command in Excel, as shown in Video 2-4 Goal
Seek Colebrook-White Example, to run the iterations for you.
Even though the Colebrook equation is generally accepted as the most accurate method for estimating
the friction factor, it is not easy to use. There are two other methods that approximate the results of
the Colebrook equation and do not require iterating. The first was developed by P.K. Swamee and A.K.
Jain (1976), and the second by S.E. Haaland (1983).
“Swamee-Jain” Equation (Eq. 2-3)
𝑓=
0.25
𝜀 ⁄𝐷 5.74
[log10 ( 3.7 + 0.9 )]
𝑅𝑒
2
“Haaland” Equation (Eq. 2-4)
1
√𝑓
1.11
= −1.8𝑙𝑜𝑔10 [(
𝜀 ⁄𝐷
)
3.7
+
6.9
]
𝑅𝑒
Each of these allow you to solve for the friction factor directly, and each (according to their research)
results in errors that are within the tolerance created by the input data.
However, solving these equation by hand is difficult and spreadsheets are not allowed on licensing
exams. Larry Moody (1944) solved the Colebrook equation by varying the inputs, then graphed the
result and published his chart. Video 2-5 Moody Chart provides an overview of how to use the moody
chart to estimate the friction factor.
13
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
As an alternative to the Darcy-Weisbach equation, Allen Hazen and Stewart Williams analyzed pipe flow
velocities in the United States and published their work in a book entitled Hydraulic Tables in 1911. The
Hazen-Williams equation is the most common method used for pipeline analysis in the US. It has been
solved many ways to make it easier to apply to American Standard Units (gal/min & inches). Video 2-6
Working with Hazen-Williams derives the most common forms of the equation so that you know the
appropriate units for Q and D to use.
Similar to Maximum velocity, each water utility may specify a maximum unit headloss for their system.
Video 2-7 Hazen Williams Examples applys two derivations of this equation to (1) assess energy loss in a
pipeline and (2) size a pipeline given a maximum unit headloss criteria just like you would do in practice.
Task 2.3 Residual Pressure
Residual pressure is the amount of potential energy remaining in a fluid contained in a pressurized
pipeline. Since water utilities are selling water and the energy, engineers must certify that the residual
pressure within the system is high enough to be delivered into the home, but not so high that it
damages the faucets and other fixtures in the home.
One of the steps to understanding residual pressure includes understanding how to visualize the
Hydraulic Grade Line (HGL) and the Energy Grade Line (EGL) in a pressurize pipeline. Video 2-8 shows
how you can draw the HGL and EGL on a pipeline profile so you can begin to understand the concept of
residual pressure.
Analyzing the residual pressure requires that we understand the principle of Conservation of Energy
which is derived in Video 2-9. Video 2-10 covers Daniel Bernoulli’s development of an expression to find
the residual pressure in a system that builds upon the law of conservation of energy.
In this task you learn how to apply the conservation of energy equation to determine if the residual
pressure at the end of the line is sufficient to meet a specified residual pressure criteria. Video 2-11
Conservation of Energy Applied and Video 2-12 Residual Pressure cover how you apply the principle of
conservation of energy to determine the residual pressure in a pipeline. In this same video, you are
introduced to two new terms: The Hydraulic Grade Line and the Energy Grade Line. These ‘lines’ help
visualize the quantity of energy throughout a pipeline rather than just thinking about the energy at a
single point.
Similar to the velocity and the unit headloss criteria, many water agencies specify a minimum residual
pressure criteria. The residual pressure criteria is defined by each agency, but typically is a determined
by the demand scenario (Maximum Day, Peak Hour, or Maximum Day Plus Fire Flow). For Maximum
Day and Peak Hour scenarios, the residual pressure criteria vary by water agency: 30 psi – 40 psi for
Peak Hour, and 40 – 60 psi for Maximum Day scenarios. The Max Day Plus Fire flow scenario must
provide at least 20 psi minimum based upon the fire code.
Minor Losses
Minor losses are the energy that is removed from the system as a result of bends in the pipeline or as
the fluid passes through valves and other flow control devices (in general we refer to fittings and valves
as “pipe appurtenances”). The friction loss for each fitting or valve is computed using the following
formula.
14
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
𝑣2
ℎ𝑚 = 𝑘 2𝑔
Eq 2-2
In this equation, k is a minor loss coefficient which is selected based upon the type of bend or valve, v is
the velocity of the fluid in the pipe, and g is the gravitational constant. A table of typical k values for
different fittings is included in the Appendix.
Example 2-1. A tank is connected to a pump (installed
below ground) through a 25-ft long, 8-inch Ductile Iron
Pipe (C = 130) as shown in Figure 2.1. Analyze the major
(friction) and minor losses for this pipeline if the flowrate is
1650 gal/min and the minor losses include an entrance loss
and a 90-degree cast elbow.
Bell Entrance
90° Cast (Regular)
P
Figure 2.1
Estimate the friction losses using Hazen-Williams
ℎ𝐿 = 𝐿 (
3.55 𝑄 1.85
3.55 (1650 𝑔𝑝𝑚) 1.85
)
=
25𝑓𝑡
(
)
= 1.16 𝑓𝑡
𝐶 𝐷 2.63
130 (8 𝑖𝑛)2.63
Solve for the velocity using continuity:
𝑔𝑎𝑙
𝑔𝑝𝑚
1650 𝑚𝑖𝑛⁄448.8
𝑄
𝑓𝑡
𝑐𝑓𝑠
𝑣= =
= 10.53
2
𝐴
0.349 𝑓𝑡
𝑠
Look up the minor loss coefficients for the entrance and 90-degree bend. KENT = 0.05; K90,CAST = 0.25
Compute the minor losses:
𝑣2
10.53 2
ℎ𝑚 = 𝑘 2𝑔 = (0.05 + 0.25) 64.4 = 0.52 𝑓𝑡
15
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
Lesson 2 Practice
1. A water agency stated that waterlines cannot have water flowing faster than 8 ft/s. What is the
minimum standard pipe diameter that can transport 1750 gal/min without exceeding this limit?
2. An existing 12” transmission main was sized to handle a design flowrate of 1550 gal/min. New
development in the area requires that this pipeline now convey 2350 gal/min. The water
agency specifies the maximum velocity cannot not exceed 7.5 ft/s. Will the existing pipeline size
be large enough to handle the flowrate and stay under the maximum velocity?
3. A 16-inch, PVC waterline has a relative roughness of 0.0003. The Reynolds number of the fluid
in the pipeline is 500,000. Using the Moody Chart, what is the friction factor?
4. A city has an old 10-inch steel waterline still in service that they installed more than 80 years
ago. The city installed monitoring equipment to determine if there was any deterioration of the
pipeline wall. During one of the tests the flowrate in a 1250-foot section of the pipeline was
metered at 1200 gal/min and showed a headloss of 11.25 feet. The temperature of the water
was 60° F.
a. What is the observed friction factor in this pipeline?
b. What is the Reynolds number for the fluid flow in the pipeline?
c. What is the relative roughness of the steel pipe?
5. Calculate the friction factor from problem 2.3 using the Colebrook-White equation and then
compare this with the result you get using the Swamee-Jain Equation and the Haaland Equation.
State the ‘error’ associated with using the Swamee-Jain Equation as well as the Haaland
equation. Use a spreadsheet to do the computations.
6. A new pipeline is installed to convey 2500 gal/min. If the pipeline can not exceed 6 ft/1,000ft of
head loss what is the minimum standard diameter to convey the flowrate? Size both PVC
(C=130) and steel (C=120) pipelines.
7. An existing 10-inch PVC line (C = 130) is designed to carry 900 gal/min. A new development
wants to use this line for their water service which means the existing 10-inch line needs to
convey an additional 500 gal/min, for a total flowrate of 1400 gal/min. The water utility
standards state that the unit headloss can not exceed 5 ft/1000 ft. Will this new development
cause the pipeline to exceed its capacity? Please show your work answering this question.
8. Figure 2-1 shows a pipeline in section view. Above the pipeline profile, conceptually draw
change of energy through the 8” pipeline by sketching in the Hydraulic Grade Line (HGL) and
Energy Grade Line (EGL). Label the changes in energy as either being a major loss (friction) or a
minor loss (fitting). NOTE: The vertical scale is exaggerated by a factor of 10 to be able to show
the diameter of the pipeline.
16
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
Figure 2.1 – Section view of proposed waterline. The ovals represent existing pipelines running
perpendicular to the waterline (into the page). The vertical scale is exaggerated by 10 to show the
thickness of the pipeline (hence the oval shape to the existing pipelines).
17
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
9. Figure 2.2 shows the plan view of a new 12-inch PVC pipeline (f = 0.019) that is 1,100 feet long
and is meant to deliver 2550 gal/min to the proposed development. Point 1 has a residual
pressure of 61.5 lb/in2. The elevation at points 1 and 2 are 850 feet and 865 feet respectively.
Compute the residual pressure (accounting for friction and minor losses) for this pipeline. Does
this proposed pipeline meet the minimum residual pressure of 30 lb/in2?
1
2
PROPOSED DEVELOPMENT
NOTE: Each of the bends are 45-degree cast fittings. At each fire hydrant location, install a tee to create
a lateral to the fire hydrant.
Plan View
Not to Scale
- Fire Hydrant
Figure 2.2 Plan view of a proposed waterline showing the location of fire hydrants along the pipeline
18
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
Lesson 2 Project
Design a water transmission main to service a new residential development. The new development has
710 single-family residential units. Use the design criteria specified by the Western Municipal Water
District (WMWD), hereafter referred to as the DISTRICT, which is available in Appendix BB.
Tasks
1. Where will your waterline be installed? Design the proposed pipeline from the existing pipe
location to the Project Site. You decide the path the pipeline will take. The CAD file associated
with this project provides the detailed alignment of the proposed pipeline.
a. Draw the pipe's centerline from the existing pipe to the future pipe connection point.
b. Include the appropriate number of valves based upon the guidelines.
c. Label each fitting and valve located along the pipeline. Examples: GATE VALVE or 90DEG BEND (MITERED)
2. What is the design flowrate? Calculate the Maximum Day + Fire Flow (MD+FF) demand for the
residential development using DISTRICT demand factors.
a. Calculate the Max Day Demand, then add 1750 gpm to account for the Fire Flow
demand
3. What is the diameter of the pipeline? Select a pipe diameter that meets the district
performance criteria for the MD+FF scenario.
a. Size the pipeline to meet the maximum velocity criteria
b. Size the pipeline to meet the unit headloss criteria using the Hazen-Williams equation
4. What is the remaining energy in the pipeline (lb/in2) at the connection point to the future
waterline? The existing pipeline has an initial pressure of 61.50 psi at Log Cabin and El Capitan.
a. Calculate the total friction losses using the Darcy-Weisbach equation (Assume T = 70deg F)
b. Calculate the minor losses in the pipeline
c. Calculate the residual pressure (psi) at the end of the pipeline.
Submission
Provide a single .docx or .pdf document listing your calculations from each task. For Task 3, show only
the calculations using the final “design” diameter. Provide a PDF of your pipeline design created in CAD.
The .dwg file provided with this assignment already has the sheet layout created in paper space.
Therefore, once you have completed your design in model space, go to paper space and ‘PLOT’ the
layouts to PDF format. Bring a hardcopy of your submission with you to class for review and grading.
19
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
Lesson 2 – Experiment No. 1
A pipe's roughness is a key point of concern when choosing a pipeline. Therefore, each pipe
manufacturer must test, periodically, the roughness of their pipelines to determine if there are any
changes to the roughness over time.
Tasks
1. Draw a schematic of an apparatus that could be used to test the roughness of a pipeline. This
apparatus should show a tank (source of water) a pump (source of energy), the pipe (of course)
and Pressure gauges to observe the loss in the pipeline. Identify the direction of flow in the
model.
2. Collect headloss data for the 3/4” PVC by watching the
NOTE: While we reference the
video on the pipe friction experiment. This video
lab manual for the procedure, DO
follows the experiment tasks outlined in Section 1,
NOT follow the task description
Experiments 1 & 2 of the Hydraulic Lab Manual.
in the lab manual. Follow only
a. Note: There are two pressure gauges used on
tasks contained here.
the friction experiment: (1) Analog gauge –
measuring “Inches of Water”, (2) Digital LED
gauges – measuring “lb/in2”. Both gauges are measuring the energy lost (i.e. headloss)
between the first port and the other pressure ports at 2’, 4’, 6’, 8’, and 10’.
3. Tabulate all data and convert units
a. discharge from gpm into ft3/s (for use in the Darcy-Weisbach Equation) and
b. headloss from “inches of water” to “feet of water”
4. Calculate f and C for each pipeline, and at each flowrate, using the head losses converted from
the measurements during the experiment. These computations can be done using the following
equations, solving them for f and C respectively.
3.55 𝑄 1.85
ℎ𝐿 = L ( 2.63 )
𝐶𝐷
Equation 2-3. The Hazen-Williams equation solved for total headloss, where Q is
the conduit flowrate in gpm, D is the pipeline diameter in Inches, and L is the
length of the conduit in feet.
ℎ𝐿 = 𝑓
𝐿 𝑉2
𝐷 2𝑔
Equation 2-4. The Darcy-Weisbach equation for friction losses of a fluid in a
pipeline, where the total headloss (hL – ft) is calculated from the friction factor
(f), the length of the pipe (L), the diameter of the pipeline (D) and the velocity
head in the pipeline (V2/2g).
5. Calculate the average f and C value for each pipeline.
6. Calculate Reynolds’s number for each pipe at each flowrate using Equation 2-5.
𝑅𝑒 =
𝑉𝐷
𝜈
Equation 2-5. Reynolds Number calculation using the pipe velocity (V – ft/s),
nominal pipe diameter (D – ft), and the kinematic viscosity of water (ν –ft2/s).
20
Hydraulic Lessons
Lesson 2: Pipeline Design & Analysis
7. Determine the ε value.
a. Obtain the ε/D value from the Moody Diagram, using the friction factor (f), and
Reynold’s number obtained in the previous steps.
b. multiply ‘ε/D’ by the diameter of the pipe to obtain ε.
8. Compare the ε and C values obtained in the experiment with the values in Table 2-3 (Jones et
al., 2008) to determine if there is any significant deterioration in the pipe wall smoothness.
Table 2-3. Probable Coefficients for Pipe Friction for the Design of Pipes Flowing Full for
Nonaggressive Water and Good Pipeline Maintenance.
Material
Plastic, FRP, and epoxy
≤ 400 mm (16 in)
Hazen-Williams C
Moody Diagram ε
(in.)
140 – 130
Smooth – 0.008
135 – 125
0.005 – 0.013
Cement Mortar Lining
≤ 400 mm (16 in)
Submission
Write a 1 - 2-page summary of the test in the format of a memo. The memo should include the
following information: The Experiment overview/purpose, Procedure (Cite the procedural steps in the
lab manual freely to avoid writing a step-by-step accounting of the experimental procedure), Analysis,
Limitations, and Conclusions.
21
Hydraulic Lessons
LESSON 3: WATER DISTRIBUTION NETWORK
Project Background
A new section of a city needs a water system installed. As water resource engineers, we certify that the
system can deliver the water demand through the system while meeting all the hydraulic performance
criteria stated by the agency. Most potable water systems are not a single pipeline, nor are they simply
pipes in parallel. They are networks or grids of pipes. Computing the hydraulic performance parameters
(velocity, unit headloss, and residual pressure) requires that we know the flowrate in each pipeline.
In this lesson we also learn to use EPANET, a hydraulic network analysis software that can help us find
the flowrate in each pipeline and compute the velocity and unit headloss in each pipe as well as the
residual pressure within the system. Once again, a successful system design means that it complies with
all of the owner/operators published guidelines.
Lesson 3 Overview
This lesson is divided into three (3) tasks: Pipes in series & parallel, three-reservoir problem, and the
Network Analysis. Each task covers a specific topic (similar to what you would receive in one or two
lectures) and includes practice problems to assess your progress. Read through each task and complete
each activity (reading, watching videos, and lesson practice). Complete each task in the order provided.
Learning Outcomes
At the end of this module you will be able to:
•
•
•
•
Solve for headloss and flowrate in a simple network
Analyze a pipe network using Excel and EPANET
Optimize a water distribution system
Estimate the costs of a water system Analyze the unit headloss and total headloss of a
pipeline
22
Hydraulic Lessons
Lesson 3: Water Distribution Network
Task 3.1 Pipes in Series & Parallel
Designing and analyzing a single pipeline, where the diameter and material never change is what you
have learned so far from the previous tasks. However, it is often the case that pipelines will change
diameter, or material along a given run and we call this "pipes in series". It is also the case that when we
distribute water to an entire city we will branch off pipes in different directions and create an entire
network of pipes. To understand how to analyze a pipe network we must first cover the basic principle
of analyzing pipes in parallel. Video 3-1 Pipes in Parallel covers both pipes in series and in parallel. After
reviewing the basic concepts, Video 3-2 Pipes in Parallel Example, walks you through how to solve such
problems by hand.
Task 3.2 Three Reservoir Problem
The 3-reservoir problem is a famous water resource engineering challenge often used in FE and PE exam
questions. The concept builds upon the basic principles that are covered in the pipes in parallel video.
The general idea is that there is a system, represented by a point, which is connected to three
reservoirs. The physical characteristics of the pipelines are typically known, the water levels in each
reservoir are known and what is left for analysis is the pressure head at the middle point, and the
flowrates into, or out of, each of the reservoirs. Because you have more unknowns that equations you
must use a numerical method to find the pressure head at D which will then lead you to solve for the
flowrates in each of the pipelines. Video 3-3 Three Reservoir problem outlines this approach. Video 3-3
Goal Seek 3 Reservoir Problem shows how to solve the problem using a spreadsheet.
NOTE: In hydraulics, a reservoir is a term used for an inexhaustible water supply that has a fixed water
level, or potential energy head.
Task 3.3 Network Analysis
In order to simply the algebra of analyzing a water distribution network, we can use the Hardy Cross
method. Rather than looking at each pipe individually, the Hardy Cross method groups pipelines in a
network into loops. This simplifies the algebra and makes it a bit easier to code the process into
software. Video 3-4 Hardy Cross Method Overview outlines this method and Video 3-5 Hardy Cross Part
2, which shows you how to setup a Hardy Cross analysis by hand. I have also attached a series of videos
that cover how to set up the analysis of a water distribution network using the hardy cross method in
Excel.
Hardy Cross Method in Excel Part 1
Hardy Cross Method in Excel Part 2
Hardy Cross Method in Excel Part 3
23
Hydraulic Lessons
Lesson 3: Water Distribution Network
Lesson 3 Practice
1. A waterline distributes water to a cul-de-sac. A total of 5 homes are connected to the water
line. Assuming that each house needs 100 gal/min, what is the total headloss due to friction at
the end of the pipeline?
P-1
200 ft
6-in PVC
C=130
P-2
90 ft
4-in PVC
C = 120
P-3
140 ft
3-in PVC
C = 120
Figure 3.1 Plan view of cul-de-sac
2. 850 gal/min enters the system at Junction A and then splits the flowrate into pipelines P-1
and P-2. At junction B the fluid combines again and exits the system. What is the flowrate in
each pipeline (QP-1 & QP-2)?
A
P-1
650 ft
8” PVC (C=90)
P-2
400 ft
6” PVC (C=150)
B
Figure 3.1 Plan view of water system schematic
24
Hydraulic Lessons
Lesson 3: Water Distribution Network
3. Find the flowrate in each pipeline (P-1, P-2, P-3). The general approach is to find the pressure
head at D (PD/γ) such that the flowrates entering D minus the flowrate exiting D is equal to 0 (QIN
– QOUT = 0).
a. Guess the pressure head at D (PD/γ + z).
b. Compute the flowrate in Pipes P-1, P-2, and P-3
c. Sum the flowrates at Pt. D.
i. If ΣQD = 0, then you are done
ii. If ΣQD ≠ 0, then repeat steps 1 – 3 again.
ZA
ZB
ZD
ZC
Pipe ID
P-1
P-2
P-3
Length (ft)
1,100
800
1,000
Point
Reservoir A
Reservoir B
Reservoir C
Point D
Diameter
(in)
8
12
6
C
100
130
120
Elevation (ft)
160
110
70
90
25
Hydraulic Lessons
Lesson 3: Water Distribution Network
Lesson 3 Project
Complete a water network analysis for the land use map included with this project. To analyze the
water network should use EPANET which is available to download for free from the EPANET Website.
Tasks
1. Create your water network model using WaterCAD or EPANET. Insert the pipes and junctions as
shown on Figure 1 (see attached spreadsheet). When completed, you should have: Nine (9)
junctions (nodes), and Thirteen (13) pipes (links).
2. Input the Physical characteristics of the network into your model. This includes entering the X,Y
Coordinates for each junction so that the model is to scale. You need to make an initial guess
for each pipeline diameter and material for every pipeline in your system. The C value will come
from the WMWD standards, and the Length for each pipeline will come from Figure 1.
3. Input the water demand at each junction as summarized in Table 1 for the Peak Hour Scenario.
Once complete, export your scenario as a .scn file (Suggested File Name: P3_PeakHour.scn).
TABLE 1. Water Network Demands Organized by Junction
Junction Elevation
AREA
Units
Av Day
Max Day Peak Hr
ID
(ft)
(ac)
Units
(gpm)
(gpm)
(gpm)
J-1
703
62.5
382.5
302.8
529.9
908.4
J-2
672
75
675.0
534.4
935.2
1603.1
J-3
676
62.5
382.5
302.8
529.9
908.4
J-4
682
75
477.5
416.8
729.3
1250.3
J-5
675
90
622.5
586.6
1026.5
1759.7
J-6
685
75
407.5
403.9
706.7
1211.6
J-7
676
62.5
260.0
284.6
498.0
853.8
J-8
679
75
652.5
520.3
910.5
1560.9
J-9
703
62.5
230.0
295.8
517.7
887.5
Network Totals
640
4,090
3,648
6,384
10,944
With Fire -->
8,134
4. Run the analysis in EPANET. Your analysis should run, but it should warn you that there are
negative pressures in the system. You should expect this because the default pipe diameter is
often 12 inches which is too small for this amount of water flowing to the different areas of the
system.
5. Optimize the pipeline diameters. This means you should change the pipeline diameters to be
just large enough to meet the max velocity, maximum headloss, and minimum residual pressure
criteria using the design criteria stated in the Western Municipal Water District.
6. Export the pipeline output table (showing pipe identification tag, diameter, flowrate in gpm,
velocity in ft/s, and unit headloss in ft/kft) as well as the junction output table (showing the
junction number, elevation, and residual pressure in psi).
Exporting the data from the tables includes selecting the values in the table, then clicking on
Edit --> Copy To --> Clipboard. Once it's on your clipboard, you can paste the data into Excel
where you can format the data to look nicer and also fit onto the page of your report.
26
Hydraulic Lessons
Lesson 3: Water Distribution Network
7. Save your scenario as 'P3_PeakHour.scn'.
8. Repeat Steps 3 through 7 for the Max Day Demand scenario. Add the FIre Flow rate of 1750
gal/min to one junction (add the fire flow amount to the max day amount already assigned to
that junction. For example - you think J-5 is the best place to assign the fire flow, which already
has a max day demand of 525 gal/min. At J-5 the total demand should be entered as 2275
gpm).
***NOTE*** If you change a pipe diameter during the Max Day Deman optimization step, then
you must also make the same change on the Peak Hour scenario, reanalyze the scenario, and reexport the data tables.
At the end of Task 8 you should have four (4) tables summarizing your results (Peak Hour Pipes,
Peak Hour Junctions, MD+FF Pipes, MD+FF junctions)
9. Estimate the cost of your proposed system (pipes & valves) using the unit costs presented in
Table 2. Start with the pipeline output table. Sum pipe lengths by diameter and apply the unit
cost. Divide the length of each pipeline by 1320 feet to estimate the number of valves required
along each pipeline.
Table 2. Summary of unit cost for typical pipes and valves
Material
Unit Cost ($) Unit
8” PVC/DIP
38 LF
12” PVC/DIP
69 LF
16” PVC/DIP
155 LF
18” PVC/DIP
205 LF
24” PVC/DIP
285 LF
30” CMLCP
515 LF
36” CMLCP
653 LF
8” GATE VALVE
600 EA
12” BUTTERFLY VALVE
750 EA
16” BUTTERFLY VALVE
1760 EA
18” BUTTERFLY VALVE
2600 EA
24” BUTTERFLY VALVE
3200 EA
30” BUTTERFLY VALVE
3900 EA
36” BUTTERFLY VALVE
4600 EA
10. Create a table summarizing the quantities of each pipeline (sorted by diameter) and valves (also
sorted by diameter) and the item cost for each diameter of pipeline and valve, as well as the
overall total cost for the water system.
11. Write a report summarizing your work. Include a brief background about the purpose of the
project and include the data from Table 1. State the criteria you are trying to meet with your
analysis. Discuss the method used to analyze the system (EPANET software, Excel, WaterCAD,
etc). Finally, provide commentary on the results of your analysis (including the cost analysis)
and state your final conclusions about the system. Include the maps of the system and the
output tables from your analysis results. Do not cite each task in your report.
27
Hydraulic Lessons
Lesson 3: Water Distribution Network
Submission
The final report should be a single .pdf or .docx file that includes all writing, figures, and tables. Be sure
to explicitly reference the Tables and Figures showing your analysis data in the text of your report. If
you do not mention each Table or Figure in your report then that tells me that the data were not
necessary.
28
Hydraulic Lessons
Lesson 3: Water Distribution Network
FIGURE 1
NETWORK NODE MAP
PROJECT NO. 3
29
Hydraulic Lessons
Lesson 3: Water Distribution Network
Lesson 3 – Experiment No. 2
Water systems mandate which types of headloss method is required for analysis in their system: DarcyWeisbach (D-W) or Hazen-Williams (H-W). Given your specific site conditions, there is a test that you
can perform to determine which method is more appropriate.
If you simplify the two headloss expressions, you get the following for (a) D-W and (b) H-W:
hL = rQ2
(a)
hL = rQ1.85
(b)
In other words, the main difference between the theoretically derived Darcy Weisbach equation and the
empirically developed Hazen-Williams equation.
For this experiment you will create a graph using Excel using the same data that you started with for
Experiment 1. The objective of this experiment is to learn to use Excel’s graphing tools to create an X-Y
Scatter Plot, add a trendline, change the format of the trendline, and display an equation for the
trendline.
Tasks
1. Organize the data. For each test run, there was a flowrate and a headloss at 2, 4, 6, 8, and 10
feet. Therefore, to graph this in excel you should organize your data as follows:
Q1 → hL @ 2 feet
Q1 → hL @ 4 feet
Q1 → hL @ 6 feet
Q1 → hL @ 8 feet
Q1 → hL @ 10 feet
Q2 → hL @ 2 feet
.
.
Q2 → hL @ 10 feet
Organize all the data into a single set of paired data like this.
2. Create the Graph. In Excel, create an X-Y scatter plot by selecting the flowrate as the “x” axis,
and the headloss as the “y” axis. Do not add a line for the data, just show the “markers” of each
data point.
a. Format both axes so that they are in log format. Label this graph Figure 1.
3. Add a trendline. In Excel, right-click on the “markers” of your X-Y scatter plot and select “Add
Trendline”.
a. In the options that appear, select Logarithmic for the Trendline Option.
b. Display the equation of the trend line on the graph. The equation should have the
following format:
log ℎ𝐿 = 𝐍 log 𝑄 + log 𝐾
y = mx + b
4. Compare your result to the published equations. Report the value of N that you obtained from
the experiment.
30
Hydraulic Lessons
Lesson 3: Water Distribution Network
Example: Let’s suppose your trendline equation is this:
y = 0.97ln(x) + 0.41
If this was your result, you would report that the N value observed in the testing as 0.97.
a. Comparison with Hazen-Wiliams Equation. In Hazen & Williams observations they
created an empirical equation where N = 1.85. In your memo, explain how your result
compares with this value.
b. Comparison with Darcy-Weisbach Equation. This equation was derived mathematically,
where they determined that N = 2. In your memo, explain how your result compares
with this value.
c. Conclusion. Discuss which headloss calculation technique appears to fit your
experimental results better. It is also acceptable to state that your result does not
match either the Hazen-Williams or Darcy-Weisbach equations.
Submission
Provide a 1 or 2-page document that includes the following information: The Experiment
overview/purpose, Procedure (Cite the procedural steps in the lab manual freely to avoid writing a stepby-step accounting of the experimental procedure), Analysis, Limitations, and Conclusions.
31
Hydraulic Lessons
LESSON 4: SELECTING A CENTRIFUGAL PUMP
Project Background
Many areas extract water from a river or groundwater source, treat the water (filter, chlorinate, etc) and
then store the water in a tank. This water is then pumped to a distribution system. Typically, we do not
pump directly to individual consumers. Rather, we pump to another storage tank at a higher elevation
and then allow the water to drain via gravity to each of the end users. This approach has two main
advantages:
1. If the power fails, then the water in the storage tank can still supply water and energy to the
system via gravity
2. Electricity during the day is more expensive than at night. Filling a tank in the off-peak hours
allows the water agency to decrease their operating costs.
The most basic pump station usually comprises of at least two pumps: one for operation (duty) and
another ready to operate in case the first fails. This allows for prolonged maintenance of one pump
while the other carries the load for the system.
As the engineer on the job, it is your challenge to design a system that can carry water from a treatment
plant’s product tank up to a system storage tank. To do that you will also have to select a pump that is
appropriate for the task.
Lesson 4 Overview
This module is divided into five (5) tasks: System Curves, Pumps and Pump Performance, Net Positive
Suction Head, Affinity Laws, and Pump Selection. Each task covers a specific topic (similar to what you
would receive in one or two lectures) and includes practice problems to assess your progress. Read
through each learning unit and complete each activity (reading, watching videos, and completing the
assignments). Complete each task in the order provided.
Learning Outcomes
At the end of this module you will be able to:
•
•
•
•
•
•
•
•
•
Describe the main anatomy and operation of a centrifugal pump
Differentiate between centrifugal pumps and other pump types
Analyze a pumping and storage system to develop a system curve
Interpret information provided on a pump performance curve
Differentiate between NPSHR and NPSHA
Explain the vapor pressure of a fluid
Calculate NPSHA
Select a pump that is appropriate for a given system curve
Predict the change in performance for a pump using the affinity laws
32
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
Task 4.1 System Curves
Before you can know what is the best pump for your system it is critical that you understand the
hydraulic situation presented by your system. "System hydraulics" refers to how the system responds to
different flowrates. The following video explains further why this is important to know as well as provide
you with the method to create the system curve equation. Video 4.1 System Curve walks you through
an example of developing a system curve using the Darcy-Weisbach equation.
Task 4.2 Pumps and Pump Performance
In this task, you will be introduced to the different kinds of pumps (albeit very briefly) and then we will
discuss the centrifugal pump in greater detail. Video 4.2 Centrifugal Pump Overview provides some
general information about centrifugal pumps and some vocabulary that is helpful to know. Video 4.3
Pump Selection Consideration shows you how to interpret data from a pump performance chart.
Task 4.3 Net Positive Suction Head and Cavitation
This task only needs to be separated from the others to emphasize that you should spend a little time on
just this concept to make sure you understand it.
When selecting a pump, the main problem encountered is cavitation and it occurs every time you
operate a pump too far outside its Best Efficiency Point. With every pump selection, you are trying to
minimize the risk of cavitation. To minimize that risk, we must design our system such that the net
positive suction head available (NPSHA) is greater than the net positive suction head required (NPSHR) by
the pump. NPSHR is provided by the pump manufacturer, while NPSHA is computed by you, the
engineer, using Eq. 4-1:
𝑃
𝑃
𝛾
𝑁𝑃𝑆𝐻𝐴 = 𝑎𝑡𝑚 + (𝑧𝑡𝑎𝑛𝑘 − 𝑧𝑝𝑢𝑚𝑝 ) − ℎ𝐿 − ℎ𝑚 − 𝑣
𝛾
In this equation, Patm is the atmospheric pressure and Pv is
the vapor pressure. When divided by the unit weight of
the fluid (with appropriate unit conversions) you obtain
the atmospheric pressure head and vapor pressure head.
We subtract the vapor pressure head to remove the
impact the vapor layer has on the suction pressure. The
amount of hydrostatic pressure on the pump is
accounted for by subtracting the pump eye elevation
from the fluid elevation in the tank (ztank – zpump). Finally,
we subtract the friction and minor losses (hL and hm,
respectively) to account for the pressure head losses as
the fluid travels from the tank to the pump suction
flange.
Video 4.4 Cavitation and NPSHa provides a brief overview
of cavitation and how we mitigate the risk of cavitation in
our pump selection. Video 4.5 NPSHa Example walks your
through an example of how to compute the NPSHa in a
system.
Eq. 4-1
Vapor Pressure
In Video 4.4 you are introduced to a new
fluid property, Vapor Pressure. Water
molecules are constantly being expelled
into the atmosphere from bodies of
water. The molecules are heavier than
air so they create a layer of vapor near
the surface of the water – like a blanket
on the surface of the water. At higher
temperatures, the vapor layer is thicker
than at lower temperatures. Water in a
tank always has a layer of water vapor
above it. Since this layer is heavier than
drier air, the water vapor layer exerts a
pressure onto the fluid surface. This
pressure is known as water vapor
pressure and can be looked up from a
table summarizing the properties of
water at various temperatures.
33
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
Task 4.4 Affinity Laws
For each pump built, we can define its hydraulic performance as a function of its physical or operating
performance. For example, we can create a dimensionless number that is custom to a given pump,
which is based upon it operating speed, and impeller diameter. This dimensionless number provide us a
tool to predict what will be the new hydraulic performance of the pump (i.e. the resulting Q and H) if we
simply change the operating speed of a pump, or if we trim the impeller diameter. Video 4.6 Affinity
Laws introduces the tools to help us calculate the impact changing the motor speed or impeller
diameter has on the flow rate and head for a given pump.
Task 4.5 Pump Selection
The most basic consideration for selecting a pump is the judging if the operating point (intersection
point of the pump and system curves) is within acceptable guidelines. Generally, we never have a
system curve cross the pump performance curve at the most efficient point (sweet spot). The typical
guideline is that the operating point flowrate can be 60% - 120% of the BEP flowrate.
Another basic selection consideration is the system’s net positive suction head available (NPSHA) is
greater than the net positive suction head required NPSHR by the pump (obtained from the pump
performance chart). In practice, we add 5 feet to the NPSHr value and then compare that to the NPSHa.
Finally, if the operating point condition is met, and NPSHa > NPSHr + 5 ft, then the final consideration to
make is which pump uses more power (brake horsepower). More power = higher cost to operate. A
conversion that will be helpful to you is 1 BHP = 0.746 kW. If you pay your own power bill, then you
know that the power company sells power in terms of kW-hr (energy consumed over a time period).
You should review Video 4.3 Pump Selection Consideration already referenced in Task 4.2.
34
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
Lesson 4 Practice
1. Develop the system curve for the system represented in Figure 4-1. Solve the conservation of
energy equation for the head added (hP) using the lower reservoir as your first reference point
and the upper reservoir as your second reference point. Neglect minor losses.
2210 ft
L = 4950 ft
D = 18 in
f = 0.018
2010 ft
2005 ft
L = 50 ft
D = 18 in
f = 0.018
Figure 4.1 Pumped-storage system schematic
a. For the system shown in Problem 1 compute the system curve using the Hazen-William
Equation. Assume that the C value for the suction and discharge pipelines is 120 for
both. Keep the length and diameter the same and neglect minor losses once again.
b. Create a graph comparing the system curves created using the Darcy-Weisbach and
Hazen-Williams approaches. Show both lines on one graph (as opposed to created two
separate graphs).
35
Lesson 4: Selecting a Centrifugal Pump
800.0
600.0
400.0
200.0
250.0
1.0
225.0
0.9
200.0
0.8
175.0
0.7
150.0
0.6
125.0
0.5
100.0
0.4
75.0
0.3
50.0
0.2
25.0
0.1
0.0
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
Efficiency
Pump Head (ft)
& NPSHR (ft)
BHP
Hydraulic Lessons
0.0
9,000 10,000
Discharge (gpm)
Figure 4.2 Performance curve for a pump with an impellor diameter of 15.75-in operating at 1750 rpm.
The solid black line represents pump performance curve, the dashed line represents the efficiency curve
(read from right vertical axis), the dotted line represents NPSHR, and the dash-dot line represents the
Brake Horsepower (BHP).
2. A system curve defined as hp = 150 + 0.15∙Q1.85. Sketch the system curve onto the pump
performance curve shown in Figure 4.2. Identify the pump Operating Point. List the
corresponding Flowrate, Q, and pump head, H. Also list the pump efficiency, NPSHR, and BHP
associated with the pump operating point.
3. Identify the Best Efficiency Point (BEP) for this pump. What is the flowrate at this point?
4. To be a good selection, the pump operating point should be 60% - 120% of the BEP flowrate.
Does this pump meet that criteria?
5. Calculate the net positive suction head available (NPSHA) for the system shown in Figure 4-1.
The design flow rate is 3,600 gpm. Assume minor losses of one rounded entrance, and one 90deg bend (cast/forged) and T = 100° F.
6. You wish to use the pump shown in Figure 4.2, but you want to replace the motor with one that
operates at 1170 rpm what will the pump operating point be if you change the motor?
7. You wish to use the pump shown in Figure 4.2, but you wish the operational flowrate to be 7100
gpm. What is the impeller diameter required meet this output?
36
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
8. Select the best pump that can deliver the design flowrate of 4500 gpm using the system curve
obtained from Problem 1. Calculate the final impeller diameter for the selected pump.
(Performance Curves, Courtesy of Fairbanks Pumps)
37
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
Lesson 4 – Experiment No. 3
A pump's performance is dynamic - reacting to the system that is, itself, reacting to the added energy
and flow from the pump. This tug and pull causes the pump performance to vary. In this experiment,
you are provided with a specific pump. This pump can operate at different speeds. The client wants to
know what is the appropriate speed for the pump to operate in order to obtain an operating point
around 35 gal/min at 22 feet of head.
Tasks
1. Watch the video for the Pump Performance experiment and record the data in Table 1.
Table 1. Observed Performance of Pump A
Speed,
Torque, Pump
Frequency
n
Q
τ
Head
(Hz)
(rpm)
(gpm)
(lb-in)
Pump
Head
Brake
HP
Temp =
Water
HP
Pump
Eff, ep
(ft)
(hp)
(hp)
(%)
(psi)
29.2
2. Convert pump pressure (psi) to Pump Head (ft) using temp of fluid and unit weight of water.
3. Compute observed Brake Horse Power (BHP):
𝐵𝐻𝑃 =
𝜏 ∙ 𝑛 ∙ 2𝜋
396,000
torque (τ) – lb-in; speed (n) – rpm
4. Compute observed Water Horse Power (WHP):
𝑊𝐻𝑃 =
𝑞𝐻
3960
Flowrate observed (q) – gal/min; head observed (H) – ft
5. Compute observed Pump Efficiency (Mechanical):
𝑒𝑝 =
𝑊𝐻𝑃
𝐵𝐻𝑃
38
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
6. Estimate the 1500 rpm and 1150 rpm performance curves using the Affinity Laws. Enter the
values for Q and H for speeds 1500 and 1150 rpm into Tables 2 and 3 respectively.
𝑄1 𝑛1
=
𝑄2 𝑛2
Table 2. Pump Performance Est. @
1500 rpm
Speed, n
Q
Pump
Head
(rpm)
(gpm)
(psi)
𝐻1 𝑛12
=
𝐻2 𝑛22
Table 3. Pump Performance Est. @
1150 rpm
Speed, n
Q
Pump Head
(rpm)
(gpm)
(psi)
1500
1150
1500
1150
1500
1150
1500
1150
1500
1150
7. Plot the Performance curves onto a single x-y scatter plot using Excel
8. Write a summary of your experiment and the recommended pump speed in a memo. Include
The graph you produced in Step 7 along with Tables 1 – 3 as an attachment to your memo.
Submission
Provide a written summary in memo format. The summary should describe the main objective of the
experiment. The summary should directly refer to each figure or table by number and thoroughly
explain the data represented. The summary should also have a clear recommendation as to which speed
is required to operate the pump.
39
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
Lesson 4 Project
Overview
A pumping system needs to be designed to fill a 3 million gallon tank in 12 hours. Figure 4.3 shows a
schematic of the pumping system. The pump station is designed such that one pump is meant for duty,
while the other pump is intended for stand-by. Assume the water Temperature is 90˚ F.
Tasks
1. (20 Pts) Size the pump suction and discharge pipelines so that they do not exceed 10 ft/s. You
must use Cement Mortar Lined and Coated (CMLCP) steel pipe (C = 120). Acceptable pipeline
diameters include 12, 16, 18, and 24 inches. No other diameters are permitted. With the
pipeline sized, determine the system curve equation using the Hazen-Williams equation.
2. (20 Pts) Plot the system curve onto the attached pump performance data sheets. Based on
these plots, read the efficiency, BHP, and NPSHR at the Operating Point for each of the pump
options. Be sure to include each pump performance curve with the system curve shown.
3. (35 Pts) Calculate the Net Positive Suction Head Available (NPSHA) for the system configuration
shown on Figure 4.4 and compare it with the Net Positive Suction Head Required (NPSHR)
supplied by the manufacturer’s data sheet for each pump. Use the Darcy-Weisbach Equation to
compute the friction headloss. Check if the NPSHA > NPSHR + 5-ft.
4. (25 Pts) Select one of the pumps based upon your results from Tasks 1 - 3. Write a short
justification of your choice and a summary of the calculations performed, the inputs used, and
the results (pipe diameter, pump model selected, NPSH calculation results) obtained. Include
the general form of the equations you used and list the input values used to perform the
calculation in addition to the results of each analysis step.
Submission
Provide a single PDF document listing your calculations and results from each task. Include the pump
performance data for each pump showing your system curve. Include a brief statement, in memo
format, that clearly summarizes your work and includes a recommendation for which pump you should
use.
Attachments
Pump System Schematic
Plan View of Storage Tank to Pump Station
Pump Performance Data
40
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
865
750
L = 5750 ft
740
See Figure 4.4
for length
Figure 4.3 Pump System Schematic for Project No. 4
41
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
0
5’
10’
SCALE: 1” = 10’
Figure 4.4 Plan view of storage tank, pump and associated piping.
42
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
12-17BHSC
1150 rpm
12.0 in
Impeller Diameter
Minimum Impeller Diameter
17.25 in
13.40 in
500
400
300
200
300
0.9
250
0.8
200
0.7
150
0.6
100
0.5
50
0.4
0
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Efficiency
Pump Head (ft)
& NPSHR (ft)
BHP
Operation Speed
Suction Flange
0.3
10000
Discharge (gpm)
10-15CHSC
1150 rpm
10.0 in
Impeller Diameter
Minimum Impeller Diameter
15.75 in
12.20 in
500
400
300
200
300
0.8
250
0.7
200
0.6
150
0.5
100
0.4
50
0.3
0
0
1000
2000
3000
4000
5000
6000
7000
0.2
8000
Discharge (gpm)
43
Efficiency
Pump Head (ft)
& NPSHR (ft)
BHP
Operation Speed
Suction Flange
Hydraulic Lessons
Lesson 4: Selecting a Centrifugal Pump
10-13BHSC
Impeller Diameter
Minimum Impeller Diameter
13.50 in
10.50 in
0.8
250
0.7
200
0.6
150
0.5
100
0.4
50
0.3
0
0
1000
2000
3000
4000
5000
Efficiency
1750 rpm
10.0 in
400.0
300.0
200.0
100.0
300
Pump Head (ft)
& NPSHR (ft)
BHP
Operation Speed
Suction Flange
0.2
7000
6000
Discharge (gpm)
12-17CHSC
1150 rpm
12.0 in
Impeller Diameter
Minimum Impeller Diameter
350.0
250.0
150.0
50.0
300
17.75 in
13.80 in
Power
0.8
250
0.7
200
0.6
150
0.5
100
0.4
50
0.3
0
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0.2
5000
Discharge (gpm)
44
Efficiency
Pump Head (ft)
& NPSHR (ft)
BHP
Operation Speed
Suction Flange
Hydraulic Lessons
LESSON 5: FLOOD DIVERSION
Project Background
Every new project requires two main certifications – a geotechnical engineer needs to certify that the
soils are suitable for the planned construction activities, and a water resource engineer needs to certify
that the site will not be flooded during a rain event. As a water resource engineer, you wear two hats:
as a scientist you define the quantity of flood waters given the specific level of risk, then as an engineer,
you come up with a plan to mitigate the risk of flooding.
In this lesson, we pick up the job after just completing an analysis that quantified the amount of
stormwater. Therefore, the primary objective of this project is to protect the project site from any
flooding by diverting the runoff around the project site.
You must design and analyze two new channels along the north and east boundary lines assuming
steady and uniform flow conditions. The new housing will be installed project adjacent to an existing
flood control channel. Because of this you must check what impact the new development is going to
have on the existing channel by analyzing it for normal depth, velocity and freeboard. Understanding
how to calculate the Freeboard requires that you understand how to classify the flow in the channel as
Subcritical or Supercritical. This in turn requires that you understand the basics of Energy in an open
channel. The following tasks are provided to help you develop the knowledge and skills needed to
complete the project.
Lesson 5 Overview
This module is divided into four (4) tasks: Open Channel Design, Energy, Analysis, and Culverts. Each
unit covers a specific topic (similar to what you would receive in one or two lectures) and includes
practice problems to assess your progress. Read through each learning unit and complete each activity
(for example reading, watching videos, and completing the assignments).
Learning Outcomes
At the end of this module you will be able to:
•
•
•
•
•
•
•
•
•
•
Define hydraulic terms about open channels such as Flow Area, Wetter Perimeter, Hydraulic
Radius, and Friction Slope.
Conceptually design a channel by selecting appropriate shape, roughness, and slope given
the topography and the design flow rate
Analyze an open channel for normal depth and velocity
Calculate the Froude number for flow in an open channel
Classify unsteady/non-uniform flow profiles
Qualitatively assess unsteady/non-uniform flow in an open channel
Calculate the sequent depths and overall length of rapidly varied flow
Analyze the length of gradually varied flow
Size a culvert for inlet control conditions
Compute the discharge over a weir
45
Hydraulic Lessons
Lesson 5: Flood Diversion
Task 5.1 Open Channel Design
In Video 5-1 Open Channel Intro, I give a basic overview of open channels and the vocabulary we use to
describe them, such as friction slope, roughness, flow area, wetted perimeter, and hydraulic radius. This
leads into an explanation of basic open channel design choices engineers make when designing a new
channel. This topic is outlined in Video 5-2 Open Channel Design.
Task 5.2 Open Channel Energy
Energy in an open channel is the same as it is in a pressurized pipe, but there are some minor
differences between the two scenarios that need to be clarified. First, we look at energy - at least
initially - as relative to the channel bed, and not to an absolute datum. You also need to understand
how to define the energy profile in an open channel given the flowrate and shape. This provides the
engineer a new design guideline: Avoid critical depth. We also use a new dimensionless number to
classify the type of flow in an open channel: The Froude Number. This new vocabulary and the analysis
procedure are discussed in Video 5-3 Specific Energy.
Task 5.3 Open Channel Analysis
After the conceptual design is out of the way, the analysis
process can begin. In Video 5-4 Open Channel Analysis, I
explain the use of the Manning equation and the manner
of iterating to find the flow depth in an open channel.
Microsoft Excel has a function called Goal Seek, which can
be used to iterate the solution for you automatically.
Video 5-5 Goal Seek Open Channel Analysis and Video 5-6
Goal Seek Open Channel Visual Basic, cover how to use
this function to analyze the hydraulics in an open
channel.
Steady & Uniform
Steady is a term used to state that the
flowrate in an open channel does not
change between two points (i.e. Q1 =
Q2). Uniform describes the conduit. If
the channel (conduit) does not change
its shape, slope, or roughness between
points 1 and 2, then we say it is uniform.
In areas with steep slopes we are often concerned with high velocity flows which have the potential to
erode the lining of our channels. In areas with flatter slopes, we are concerned that the flow might
overtop the banks of the channel and flood the adjacent property. Therefore, when we do analysis of an
open channel our design criteria often address these three hydraulic parameters:
•
•
•
Normal depth (depth at steady/uniform flow)
Critical Depth & Froude Number (Energy)
Velocity
Steady Uniform Flow in Circular Channels
Pipelines installed underground are also considered open channel flow if there is a free water surface in
the pipeline (i.e. the pipe is not completely full). Using the iteration approach on circular pipes is a little
bit more complicated, so we utilize a slightly different approach that is covered in Video 5-7 Circular
Channels.
46
Hydraulic Lessons
Lesson 5: Flood Diversion
Task 5.4 Culverts
A culvert is the name for a hydraulic passage beneath a structure. The most common use for culverts is
to allow a creek or stream to flow under a road without the cost of building a bridge. Video 5-8 Culvert
Overview 1 and 5-9 Culvert Overview 2 provide more details about this type of hydraulic structure.
Video 5-10 Culvert Analysis covers a simplified view of culvert analysis. I use the term simplified
because it only focuses on the inlet control conditions of the culvert using the orifice flow equation. This
video will help you determine the appropriate size for a culvert if you know how much ponding depth at
the culvert inlet you are willing to permit.
Task 5.5 Weirs
Weirs are structures that act like dams which increase the depth of water upstream and force the water
to flow over the structure. As the flow passes over the weir structure it creates a critical flow section
which allows the amount of water flowing over the weir to be measured as a function of how high the
water is above the weir. As a result, we often see weirs employed in the following two situations:
a. Measuring the flowrate in an open channel
b. Forcing the pond depth upstream of the weir to meet a specific water surface elevation
c. Allowing water to pass over a dam into an emergency spillway.
The capacity of a weir (Bos, 1976) is often described using the following general equation:
𝑄 = 𝐶𝑤 𝐿𝐻𝑤 𝑥
Eq 5-1
Cw is the discharge coefficient, L is the length of the weir, Hw is the height of the water above the weir,
and x represents a factor related to the type of weir used.
This equation is derived from the critical depth formula which for a rectangular channel. When x = 3/2,
this equation can be modified to compute the discharge over sharp crested weirs, as follows:
𝑄 = 𝐶𝑤
2
𝑏 𝐻1.5 √2𝑔
3
Eq 5-2
Here, the length of the weir is replaced with b to denote the width of the notch in the weir. Sharp
crested weirs include straight edge, square notch and cipoletti shapes as shown in Figure 5-1.
(a)
(b)
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Hydraulic Lessons
Lesson 5: Flood Diversion
(c)
(d)
Figure 5-1. Configurations of different weirs. (a) Rectangular, (b) V-notch, (c) Cipoletti, and (d) Squarenotch
For a V-notch weir, the length of the weir is a function of the notch angle, θ. Also, for v-notch weirs, x =
2.5. These substitutions create equation 5-3.
8
𝜃
𝑄 = 𝐶 15 𝐻 2.5 √2𝑔 𝑡𝑎𝑛 2
Eq 5-3
Apart from dam spillways and measuring streamflow, almost any object can become a weir. For
example: When water is entering a culvert, but the inlet of the culvert is not fully submerged, this is
weir flow. In this case, the part of the pipe entrance in contact with the water is the length of the weir,
b, while the depth of flow above the pipe invert is H.
(a)
(b)
Figure 5-2. Section views of culvert inlets when (a) the inlet is not submerged and the analysis assumes
weir flow, and (b) when the entrance is submerged, and the analysis assumed orifice flow.
Another common application for weirs is estimating the depth of flow over a roadway. Some river
crossings are designed to have a smaller peak flowrate pass under the road through a culvert while any
extreme flooding event is designed to pass over the roadway. When a roadway becomes a weir, the
length of the weir is the portion of the road that is estimated to be ‘wet’ as water flows over the
roadway.
48
Hydraulic Lessons
Lesson 5: Flood Diversion
Lesson 5 Practice
Depth (ft)
1. A rectangular concrete (n = 0.015) open channel with base width of 5-feet is proposed with a new
flood control project. Assuming that the design flowrate is fixed at 120 ft3/s:
a. Plot the elevation head for the channel (Elevation head, EP = y)
b. Plot the velocity head for the channel (Velocity head, EK = V2/2g = Q2 /2gA2 )
c. Plot the specific energy curve for the channel (specific energy = EP + EK)
d. Calculate the critical depth for this channel and compare with the graph you create.
Energy (ft)
2. Compute the normal depth in a rectangular concrete open channel (n = 0.015) with a base width
of 6 feet that is sloped at 1.0% that is designed to convey a flowrate of 90 ft3/s.
Note: This solution requires an iterative approach.
3. Size a reinforced concrete pipe (RCP) assuming n = 0.013 pipeline that can carry 20 ft3/s. The
slope of the proposed pipeline is 0.025 ft/ft.
4. A 36" RCP (n=0.015) conveys 9.7 ft3/s at a slope of 1.5%.
a. Calculate the depth of flow in the pipeline
b. Calculate the velocity of flow in the pipeline
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Hydraulic Lessons
Lesson 5: Flood Diversion
5. A rectangular channel (b = 8 feet) crosses beneath a roadway inside a 60-inch RCP culvert
(Rounded Edge w/headwall - C = 0.50).
a. If the design flow rate is 190 ft3/s what is the headwater depth, H.
b. Provide a scaled profile view of the channel entering the culvert along with the
dimension for the headwater depth.
6. Three 3 x 3 Reinforced Concrete Boxes (RCBs), plain end with headwall (C = 0.50) are installed to
pass a design flowrate of 275 ft3/s.
a. If the culvert is installed at an invert elevation of 500.00 what is the water surface
elevation at the entrance into the culvert? (HINT: Water surface elevation, WSE is not
equal to the Headwater depth, H).
b. Provide a scaled profile view of the channel showing the culvert with the invert and the
water surface elevation labeled.
7. A culvert needs to be sized for a channel passing under a roadway. The design flowrate is 250
ft3/s. For sizing criteria, the headwater depth cannot exceed 2.0 times the diameter of the
culvert diameter. The chosen culvert entrance coefficient is 0.50. Assuming you use an RCP
what is the minimum culvert diameter using:
a. One Barrel
b. Two Barrels
c. Three Barrels
8. Compute the discharge observed at a v-notch weir. The weir has an angle of 90-degrees. The
height above the weir is 3 inches.
9. A culvert passes under a temporary access road but any excess water not passing under must go
over the road. The culvert pond depth upstream of the road is 905, but the road crown is set at
904. How much water will over-top the roadway? Assume the roadway section being
overtopped is 110 feet and that 3.2 is the weir coefficient for the roadway.
10. A stormwater detention basin has an emergency spillway to discharge the Probable Maximum
Flood (PMF) flowrate event. The PMF flowrate is 9,500 ft3/s. The elevation of the top of the
berm is set at 1250 feet. The weir needs to be set such that height above the weir does not
exceed 4-feet. Find the length of the weir. Also, sketch the flow over the weir assuming a 1.5foot freeboard between the surface of the water and the top of the detention berm.
50
Hydraulic Lessons
Lesson 5: Flood Diversion
Lesson 5 Project
Overview
A new subdivision requires protection from flooding. The hydrologic analysis is complete and now it is
time to design diversion channels around the site, analyze the existing channel and then design and
analyze culverts at the project entrance. These computations are best completed in a spreadsheet. A
sample calculation is attached to the assignment to demonstrate how you may organize your
spreadsheet.
Tasks
1. In the existing concrete channel find the normal depth and flow velocity then calculate the
required Freeboard using the flowrate computed at CP3 shown on Figure 1.
Freeboard for supercritical flow: 𝐹𝑏 = 1.0 + 0.025 𝑣(𝑦𝑛 )1/3
Freeboard for subcritical flow: 𝐹𝑏 = 0.5 + 𝑣 2 ⁄2𝑔
NOTE: Add the flow depth and the Freeboard depth together to obtain the total
channel depth and total channel width.
2. Along the north and east boundary lines of the project there is a 20-foot wide utility easement
(a strip of land that is dedicated for utilities). You must design channels to divert the flow around
the project site by picking the shape, slope, and material for each channel. The design flowrates
for the north and east channels are CP1 and CP4 respectively.
a. Calculate the normal depth
b. Calculate the flow velocity
c. Calculate the Freeboard for the north and east channels.
3. Size the proposed culverts No. 1 and No. 2 as shown on the proposed conditions drainage map
using the flowrates at CP2 and CP3 respectively. Size the culverts such that the pond depth does
not exceed 1.5 x the culvert diameter or box height. Provide separate calculation sheets
analyzing both culverts.
Submission
Provide a cover sheet followed by a table summarizing your calculations including columns for
Geometry, (bottom width [b], length [l], slope [S], and design flowrate [Q], and velocity [V]). Also include
your values for normal depth and velocity in each of the channels. Finally, include three (3) sketches
(one for each channel), each showing the channel cross section with the geometry dimensions, normal
depth, critical depth and freeboard labeled for the west, north, and east channels.
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Hydraulic Lessons
52
Hydraulic Lessons
Lesson 5: Flood Diversion
53
Hydraulic Lessons
Lesson 5: Flood Diversion
SAMPLE CALCULATION 1 – Normal Depth Analysis
54
Hydraulic Lessons
Lesson 5: Flood Diversion
SAMPLE CALCULATION 2 – Culvert Sizing Analysis
55
Hydraulic Lessons
LESSON 6: OPEN CHANNEL MODELING
Project Background
While steady/uniform analysis can help you do a lot of engineering, there are many applications where
knowing how to analyze non-uniform flow can be helpful. Take for instance the new project site in
Lesson 5. The existing open channel will be modified with the installation of the two culverts. While the
normal depth and culvert inlet analyses were helpful, computer models can provide a more accurate
representation of the entire water surface profile in a non-uniform channel. As part of this analysis, we
also learn to analyze the depth of flow over a weir.
Lesson 6 Overview
This module is divided into four (4) tasks: Non-Uniform Flow, Rapidly Varied Flow, Gradually Varied
Flow, Weirs. Each unit covers a specific topic (similar to what you would receive in one or two lectures)
and includes practice problems to assess your progress. Read through each learning unit and complete
each activity (for example reading, watching videos, and completing the assignments).
Learning Outcomes
At the end of this module you will be able to:
•
•
•
•
•
Classify unsteady/non-uniform flow profiles
Qualitatively assess unsteady/non-uniform flow in an open channel
Calculate the sequent depths and overall length of rapidly varied flow
Analyze the length of gradually varied flow
Determine the flow depth over a weir
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Hydraulic Lessons
Lesson 6: Open Channel Modeling
Task 6.1 Non-Uniform Flow
In reality, steady, uniform flow is a an ideal analysis scenario we rarely see in real life. Channels change
direction, slope, material, shape, and each of these can have an impact on the hydraulics of the channel
by creating backwater (water backing up into the channel) or tail water effects (water tailing off
downstream as it accelerates). The first step to understanding these effects is to qualitatively assess an
open channel’s water surface profile given the changes in the channel. Video 6-1 Non-Uniform Flow
provides an overview to visualizing and classifying non-uniform flow in and open channel where the
slope is changing. Video 6-2 Non-Uniform Flow 2 provides additional of non-uniform flow in a more
realistic scenario.
Task 6.2 Rapidly Varied Flow Analysis
Breaking up non-uniform flow into its two major components, we start by analyzing Rapidly Varied Flow
(RVF). RVF occurs when you transition from supercritical flow to subcritical flow. The analysis tools we
use here are empirical. Video 6-3 RVF Analysis outlines the empirical methods to estimate the sequent
depths of a hydraulic jump as well as determine the length of a hydraulic jump.
Task 6.3 Gradually Varied Flow Analysis
Here I introduce the two main methods for assessing gradually varied flow (GVF) in an open
channel: The Standard Step, and the Direct Step methods. The Standard step is used in prismatic
channels while the Direct Step is used for natural, irregular shaped channels. Video 6-4 GVF Analysis
covers these methods conceptually so that you can understand how this process could be completed by
hand and to understand how the computer software is programmed.
57
Hydraulic Lessons
Lesson 6: Open Channel Modeling
Lesson 6 Practice
1. Sketch the water surface profiles for the channels shown below. If no other control
(obstruction) is specified, assume that the normal depth is the boundary condition at the
beginning and end of the channel.
LEGEND
Normal Depth
Critical Depth
Channel Bed, or Channel Obstruction (Vertical)
Ponded Water Surface
58
Hydraulic Lessons
Lesson 6: Open Channel Modeling
2. A hydraulic jump occurs in a steep, rectangular concrete channel (n = 0.015 | b = 7 feet) with a
slope of 1.5%. If the normal depth upstream of the jump is 1.75 feet, what is the depth of flow
downstream of the hydraulic jump?
3. A hydraulic Jump occurs in a mild, rectangular concrete channel (n = 0.014 | b = 8 feet) with a
slope of 0.2%. If the normal depth downstream of the jump is 6.30 feet, what is the depth of
flow upstream of the hydraulic jump?
4. What are the lengths of the hydraulic jumps analyzed in Problem 2 and 3?
5. A steep channel transitions to a mild section. The grade change in the channel occurs as STA
11+50.00. The M3 curve was previously analyzed and determined to be 210 feet long. The
hydraulic jump was determined to be 24.5 feet long. Provide a sketch showing the channel
slope transition and the water surface elevation through the transition (including the normal
depth in the steep section, the M3, the hydraulic jump and the normal depth in the mild
section). Label the stationing of each control point. Reminder: Channel Stationing starts
downstream and increases moving upstream.
59
Hydraulic Lessons
Lesson 6: Open Channel Modeling
Lesson 6 Project
Overview
In Project 5 we assumed steady flow and uniform geometry conditions for all open channels. However,
that is not always a sufficient approach. Consider the existing channel along the western boundary of
the project site. This channel has two obstructions: the two culvert crossings to allow traffic into the
new neighborhood. These obstructions create a backwater effect in the channel that may cause the
water surface elevation to exceed the normal depth (which was computed in Project 5). To obtain a
better estimate of the channel depth, this project shows you how to model the channel and the culverts
in HEC-RAS – the River Analysis System (RAS) developed by the Army Corps of Engineers Hydrologic
Engineering Center (HEC) in Davis, CA.
Task
1. Start by building the open channel in HEC-RAS. Create a trapezoidal channel with 3:1 side
slopes, 15-ft base width and concrete lining (n = 0.015). The slope of the channel can be pulled
from the topographic map provided in Lesson 5 Project.
2. Insert the two culverts into the model. The only unknown at this point is the size of the culvert.
Make a starting guess as to the size of the culvert. The culvert should not exceed the width
available in the channel or exceed the height of the roadway.
3. Re-compute the hydraulics in the open channel each time you change the size of the culvert.
Try to find the smallest culvert (diameter of pipe, or rise & span of box) needed to ensure the
water does not overtop the roadway at both locations.
Submission
Provide a summary of your work showing the plan view of the open channel and the section view
produced by HEC-RAS showing the water surface elevation along the length of the channel. Also,
provide a written memo stating the size of each culvert. Address the memo to your instructor as the
client.
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Hydraulic Lessons
REFERENCES
LESSON 1
LESSON 2
Brown, G. O. (2003). The history of the Darcy-Weisbach equation for pipe flow resistance.
In Environmental and Water Resources History (pp. 34-43).
Colebrook, C. F. (1938–1939). "Turbulent Flow in Pipes, With Particular Reference to the Transition
Region Between the Smooth and Rough Pipe Laws". Journal of the Institution of Civil Engineers. London,
England. 11: 133–156.
Haaland, SE (1983). "Simple and Explicit Formulas for the Friction Factor in Turbulent Flow". Journal of
Fluids Engineering. 105 (1): 89–90. doi:10.1115/1.3240948.
Williams, G. S., & Hazen, A. (1908). Hydraulic Tables: The Elements of Gagings and the Friction of Water
Flowing in Pipes, Aqueducts, Sewers, Etc. as Determined by the Hazen and Williams Formula and the
Flow of Water Over Sharp-edged and Irregular Weirs, and the Quantity Discharged, as Determined by
Bazin's Formula and Experimental Investigations Upon Large Models. J. Wiley & sons.
Moody, L. F. (1944), "Friction factors for pipe flow", Transactions of the ASME, 66 (8): 671–684
Swamee, P.K.; Jain, A.K. (1976). "Explicit equations for pipe-flow problems". Journal of the Hydraulics
Division. 102 (5): 657–664.
LESSON 3
Cross, H. (November 1936). "Analysis of flow in networks of conduits or conductors". Engineering
Experiment Station. Bulletin No. 286.
LESSON 4
Jones, G. M., Bosserman, B. E., Sanks, R. L., & Tchobanoglous, G. (Eds.). (2006). Pumping station design.
Gulf Professional Publishing.
LESSON 5
61
APPENDIX A
Water System Development Guidelines
Western Municipal Water District
Irvine Ranch Water District
Appendix A
Water System Development Guidelines
Western Municipal Water District
2.0 Design Criteria for Water Distribution Systems
(Downloaded from: http://www.wmwd.com/DocumentView.aspx?DID=239)
Water system improvements proposed for inclusion into Western’s service area shall be designed in
accordance with all appropriate AWWA standards, include all landscape demands for non-residential
common areas, (i.e., landscape slopes, medians, parks, detention basins, etc.), have those demands
integrated into the demand calculations, and maintain the following criteria
2.01 SYSTEM DEMAND CRITERIA FOR TRACT DEVELOPMENT
Western’s staff reserves the right to determine criteria for each water system or sub-system based upon
conditions that may exist for that particular location, anticipated level of development, planned use or
other criteria. In general, however, water pipelines, tanks, pump stations, pressure reducing stations
and appurtenances shall be sized to handle the highest demand on the system within the sphere of
influence and shall provide capacity for the following conditions:
1.
The peak hour demand.
2.
The maximum daily demand plus fire flow.
3.
Tank refill, if required.
Average day domestic demand shall be 300 gallons per capita per day (gpcd) on annual average, with 3.8
residents per house for 1140 gpd/unit. Assume maximum daily flow of 175% of average day flow and
maximum hour flow of 300% of average day flow.
Fire flow requirements shall be in accordance with the specification of the Fire Protection Agency having
jurisdiction, e.g. Riverside County, City of Riverside, or City of Murrieta.
Commercial and industrial development proposed use and demand requirements should be reviewed
and approved by Western prior to any system analysis being performed.
Water pipelines to all service areas shall be looped to provide dual direction supply and system
flexibility. Dead end mains are undesirable, but can be considered on a case-by-case basis.
2.02 SYSTEM ANALYSIS
The proposed water system shall be analyzed for the following three conditions:
1.
2.
3.
Peak hour demands with wells/booster pumping plants on. For the peak hour demand flow
analysis, the pressure at each node shall be a minimum of 40 psi and a maximum of 120 psi.
Maximum day demand plus fire flow with wells/booster pumping plants off. For the
maximum day demand plus fire flow analysis, fire flow should be selected for the worst-case
scenario (typically the hydrant furthest from the connection(s) to Western's distribution
system, at the highest system elevation) and as directed by Western’s staff. The pressure at
each node shall be a minimum of 20 psi and the maximum velocity in the pipelines shall be
7.5 feet per second, (certain exceptions may apply).
Minimum hour demands (10% of maximum day demand) with wells/boosters on. For the
minimum hour demand analysis, the maximum velocity in the pipelines shall be 5.0 feet per
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second and the maximum pressure at each node shall be 120 psi. The Developer’s engineer
will be required to submit an analysis of anticipated flow demands; average, maximum hour
flow, and maximum day plus fire flow. Western shall accept or request modifications to the
submitted analysis.
2.03 WATER PIPELINE SIZING CRITERIA
Minimum size water pipeline is 8-inch nominal diameter, 10”, 14”, and 20” pipelines are no longer
utilized by Western.
For maximum hourly flow; pipeline to be sized to provide head losses not to exceed 3.5 feet per 1000
feet of water pipeline.
For maximum daily flow plus fire flow; pipeline to be sized to provide head losses not to exceed 5 feet
per 1000 feet of water pipeline.
For all cases, mainline velocities are not to exceed 7.5 feet per second.
Use a “C” valve of 130 for polyvinyl chloride pipe and 120 for cement mortar lined steel pipe in the
Hazen-Williams formula.
Provide a minimum of 40-psi pressure at the meter to each and every customer service using the pad
elevation of the water tank, at half-full, serving the area as the starting hydraulic grade line. Fire
hydrants are to have 20-psi minimum residual pressure at design capacities. If any service at the meter is
proposed to be less than 50 psi Engineer shall submit calculations demonstrating actual pressure at all
fixtures being supplied by that meter. Services less than 40 psi at meter will require a low pressure
service agreement.
2.09 VALVES
Location:
Large water pipelines (16-inch diameter and larger): To be determined for each system to meet
operational requirements.
Small water pipelines (12-inch diameter and smaller): To provide flexibility of operation, generally
located on discharge side of pipeline connections; 4 at crosses, 3 at tees and at beginning of dead end
mains.
If one of the options above does not apply, valves shall be spaced at 1,320-foot, maximum, intervals or
as directed by Western.
Valve spacing shall be that no more than 20 lots are to be out of service at one time.
At all times the maximum spacing to in-service fire hydrants shall not exceed 700 feet.
Size:
Full line size gate valves through 12-inch. For 16-inch and larger, use full line size butterfly valves.
Maximum velocity through valves normally limited to 12 feet per second, never to exceed 20 feet per
second.
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Unless otherwise provided for, all valves 2” through 12” shall be resilient seat gate valves in accordance
with AWWA Standard C509.
Valves shall be installed with valve can and cover as shown on Western’s Standard Drawings. Pressure
class rating shall be the same as the water pipe on which the valve is being installed.
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IRVINE RANCH WATER DISTRICT (IRWD)
SECTION 3
DESIGN CRITERIA, DOMESTIC WATER FACILITIES
The following sections are design criteria to be used in the design of domestic water systems. The
developer and his engineer shall be responsible to ensure that designs submitted are consistent with the
IRWD Rules and Regulations, Section 2 of this manual, and generally accepted standards of good
engineering practice.
3.1
Main Line Sizes
The typical minimum size distribution main pipes shall be 8-inch AWWA C-900 PVC, SDR-14, Class 200,
unless otherwise noted and approved. On short cul-de-sac dead-end mains 4-inch (with a maximum of
ten (10) each, 1-inch services) or 6-inch (with more than ten (10) each, 1-inch service lines) lines may be
allowed, however, 8-inch size main must be used to the last fire hydrant.
Developer facilities will be water mains 10-inch diameter and smaller, capital facilities will be water
mains 12-inch diameter and larger as defined by the District’s Master Plan or SAMP and will be designed
and constructed by the District.
Developer facilities will be designed by the developer and transferred to the District upon satisfactory
completion of final inspection by means of a “Bill of Sale”, Figures 5 and 8 in Chapter 2.
3.2
Design Flows
All design flows shall be based on the demands indicated in the applicable local “Sub-Area Master Plan”
(SAMP) and the Water Resources Master Plan. Where design flows are not covered by a current SAMP,
consult with IRWD’s Planning & Water Resources Department staff to review and calculate the
developer’s estimated water demands for the proposed development.
3.3
Depth of Cover
Distribution mains, 10-inch and smaller, shall have a minimum of 42 inches of cover between the top of
the pipe and the finished street grade unless shown differently on the improvement plans or otherwise
directed by the District Inspector due to unusual field conditions. Transmission mains, 12-inch and
larger, shall have a minimum of 48 inches of cover between the top of the pipe and the finished street
surface unless shown differently on the improvement plans or otherwise directed by the District
representative due to unusual field conditions. Storm drain systems must be designed with sufficient
cover so that the water mains and service laterals can be built over the top of the storm drain
mainline and laterals.
3.4
Standard Location
Domestic waterline centerlines shall be located six (6) feet from the face of the curb for all pipelines 12inches in diameter and smaller; and shall be eight (8) feet from the face of the curb for pipelines 16inches in diameter and larger. Water lines will not be allowed within easements in residential lots. There
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must be a separate lettered lot, minimum width 15 feet, if a water line needs to go outside the public
street right-of-way from cul-de-sac to cul-de-sac or from cul-de-sac to open space of tract common area.
Where water pipelines are designed to cross perpendicular beneath retaining walls or other structures
(specific written permission required for each instance), the pipeline shall be constructed in a steel pipe
casing of sufficient size and thickness (per IRWD’s Construction Manual) and with a minimum vertical
clearance of at least one (1) foot from the footing or structure itself.
3.5
Valve Arrangements
There shall be two control valves at each tee intersection of two distribution mains. If the two
distribution mains cross there shall be three (3) valves and, at major distribution points, there shall be
four (4) valves. On long blocks, intermediate valves shall be installed so that no more than twenty-eight
(28) dwelling units, six hundred (600) feet of main, or two (2) fire hydrants will be out of service at any
time. Additional looping of main lines may be necessary to satisfy this condition and the arrangement of
valves within the distribution system will be reviewed to identify the optimum network layout.
A valve must be placed at each end of an easement where a water line passes through easements
outside the traveled streets.
3.6
Separation Criteria for Water, Sewer, and Recycled Water
3.6.1 Horizontal Separation
State Health Department regulations require a 10-foot minimum horizontal separation between
domestic water and recycled water or sewer lines. There are special construction methods
which may be used where this separation cannot be achieved. Refer to the District Construction
Manual and District Standard Drawings therein. Separation other than the Health Department
minimums must be approved by the District Engineer.
3.6.2 Vertical Separation
Water, sewer, and recycled water lines are typically located vertically from the street surface
down in order of decreasing quality. Water will be the shallowest and sewer mains will be the
deepest. Refer to the District Construction Manual and District Standard Drawings therein
3.7 Fire Flow Requirements
The design requirements for fire flow will be determined by the Orange County Fire Authority (OCFA) or
the appropriate local fire jurisdiction for the specific area under development. Any plan submitted for
second plan check must have been reviewed and approved by the OCFA or the local fire jurisdiction. The
signature of the OCFA Marshal or local fire department representative on the plans shall constitute the
only form of accepted approval of the fire protection system provided.
3.8 Water Service Materials and Sizes
Approved materials and manufacturers for various service materials and connections are listed in the
Standard Specifications sections contained in the District Construction Manual. The minimum domestic
service size shall be 1-inch and made of copper tubing. Service sizes will be shown on the plan. Service
sizes available are 2” (which shall be copper), 4”, 6”, 8” and 10”; no other sizes will be allowed.
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3.9 Water Meters
All water meters will be furnished by the District subsequent to payment of all applicable fees and
posting of all required bonds. Temporary water meters (up to 3-inch in diameter) shall be applied for
through the IRWD Customer Services Department. Larger (4-inch and greater) diameter temporary
services shall be requested through the Development Services Section of the Engineering & Construction
Department with a proper engineering plan set. Refer to the District’s “Procedure For Temporary
Construction Meters”.
3.10
IRWD Standard Domestic Water Notes
The following Standard Water Notes shall be included on all improvement plans for the installation of
domestic water systems:
A.
All water system work shall conform to the District’s “Procedural Guidelines and General
Design Requirements” and “Construction Manual”, as last revised.
B. A pre-construction conference of representatives from affected utilities, agencies and the
contractor shall be held on the job site (or a location approved by the District) at least fortyeight (48) hours prior to the start of work.
C. The District Engineering Office shall be called for inspection forty-eight (48) hours before start of
work at (949) 453-5615 or (949) 453-5300. D. The proposed water system is to be staked at a
minimum 50-foot stationing if there are no existing curbs.
E. Water meters shall not be located within a driveway or sidewalk. All water service laterals shall
be constructed perpendicular to the water main without bends or angles from the connection
point on the main.
F. All main line valves shall be maintained so as to be accessible during tract development and
construction. All valve stem tops having over 60-inches of cover require an extension meeting
District standards.
G. In residential streets, the top of the pipe, 10-inches and smaller, shall be a minimum of 42inches below the finished street surface and 48-inches below finished street surface for all pipe
12-inches in diameter and larger.
H. All fire hydrants shall be set with the bottom flange 4-inches above the concrete pad or sidewalk
using one scored-spool as indicated in the Construction Manual and shall be located a minimum
of 3 feet from the ECR or BCR at intersection.
I.
All water mains 4-inches through 12-inches shall be SDR-14 or thicker and shall not be rated less
than pressure class 200, AWWA C-900 PVC, unless otherwise approved by the District.
J.
No “hot-taps” or other tie-in connections shall be made to existing District water mains prior to
conducting and passing an approved pressure test and a bacteriological test on the new water
distribution system.
K. Tapping sleeves, where called for on the plans, shall be pressure tested in an approved manner
in the field, in the presence of the District representative, prior to tapping the main line. Tapping
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Water System Development Guidelines
of the main line shall not proceed unless a District representative is present. Size on size taps of
water mains are not allowed.
L. Where meters and meter boxes are located within slopes, the angle meter stops shall be located
such that the meters and boxes are parallel and flush, with the finished surface. Wherever the
surrounding grade exceeds eight (8%) percent, or in the opinion of the District representative,
the adjacent slope is too great, a small retaining wall, clear of the meter box, shall be
constructed to the satisfaction of the District representative.
M. Curb faces shall be inscribed with the letter “W” indicating locations of all domestic water
services. Letter inscription shall be made using a 4-inch power tool wheel grinder.
N. Individual pressure regulators are required by the Uniform Plumbing Code if average static
pressure in the main is 80 psi or more.
O. Curbs shall be inscribed with tie downs for all valve locations. Letter inscriptions shall be made
using a 4-inch power tool wheel grinder.
P. The contractor shall expose all points of connection to the existing domestic water system for
verification of horizontal and vertical location before construction.
Q. Final Inspection for waterlines must include water samples that will be tested for the presence
of bacteria, conductivity, turbidity and odor. The turbidity must be less than 2.5 NTU and the
odor must be less than 1.0 TON, not to include chlorine odor, to be acceptable. Two (2)
consecutive “passing” samples are required for acceptance.
R. The contractor working on IRWD waterlines must have a C-34 license issued by the State
Contractor’s License Board or Class “A” General Contractors license (with special approval of the
District, based upon actual water and sewer pipeline construction experience.)
S. Contractor shall obtain and show proof of a construction dewatering permit from the state of
California, Regional Water Quality Control Board prior to the start of construction.
T. All butterfly valves 12-inches in diameter and larger shall be flanged and shall be bi-directionally
tested with the operator installed in accordance with the District’s requirements outlined in the
Construction Manual.
3.11 Miscellaneous Standard Guidelines
A. Separate quantity estimates are to be included on the plans to indicate quantity of pipe, number
of hydrants, valves, fittings, services, meter boxes, etc.
B. The plans shall show, in plan and profile views, the position of all other known existing
underground utilities as well as proposed underground utilities. Vertical clearance at crossings
shall be indicated by showing top of pipe and bottom of pipe elevations at the point of
intersection.
C. Temporary flush-out assemblies shall be installed at the end of all mains and large service stubouts for testing and flushing purposes.
A-7
Appendix A
Water System Development Guidelines
D. Air and vacuum relief valves shall be installed at all high points of water mains in accordance
with the District Construction Manual.
E. Water sample stations shall be provided for each contiguous water service area. Where there are
separate pressure zones, a separate water sample station shall be provided for each zone in a
location approved by the District.
F. Water mains to be constructed in landscape slopes and within easements shall be constructed
with C-900 or C-905 class 200 PVC pipe. Slope anchors may be required in accordance with the
District Construction Manual dependent upon the grades and local soil conditions. Thrust blocks
will also be required at the angle points at both top and bottom of the slope.
A-8
APPENDIX B
Hydraulic Reference Tables
By Original diagram: S Beck and R Collins, University of Sheffield (Done by the second law at English Wikipedia) Conversion to SVG:
Marc.derumaux - File:Moody_diagram.jpg, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=52681200
Moody, L. F. (1944), "Friction factors for pipe flow", Transactions of the ASME, 66 (8): 671–684
Appendix B
Hydraulic Reference Tables
B-1
Appendix B
Hydraulic Reference Tables
MINOR LOSS COEFFICIENTS
Description
k
FITTINGS
BEND (CAST) - 45°
BEND (CAST) - 90°
BEND (CAST) - 90° (LONG)
BEND (MITERED) - 15°
BEND (MITERED) - 22.5°
BEND (MITERED) - 30°
BEND (MITERED) - 45°
BEND (MITERED) - 60°
BEND (MITERED) - 90° (1 X MITER)
BEND (MITERED) - 90° (2 X MITER)
BEND (MITERED) - 90° (3 X MITER)
ENTRANCE - Bellmouth
ENTRANCE - Projecting
ENTRANCE - Rounded
ENTRANCE - Sharp-Edged
EXIT
TEE (BRANCH FLOW)
TEE (LINE FLOW)
VALVES
GATE VALVE (KNIFE - METAL SEAT)
GATE VALVE (KNIFE - RESILIENT SEAT)
GATE VALVE (DOUBLE DISC)
GATE VALVE (RESILIENT SEAT)
PLUG (LUBRICATED)*
PLUG (ECCENTRIIC, RECTANGULAR 80%)
PLUG (FULL BORE OPENING)
GLOBE VALVE*
DIAPHRAGM OR PINCH*
CONE
BALL
BUTTERFLY (25-LB CLASS)
BUTTERFLY (50-LB CLASS)
BUTTERFLY (150-LB CLASS)
REDUCER (CONICAL)
INCREASER (CONICAL)
0.18
0.25
0.18
0.05
0.01
0.10
0.20
0.35
0.80
0.30
0.30
0.05
0.80
0.25
0.50
1.00
0.75
0.30
0.20
0.30
0.15
0.30
0.75
1.00
0.50
5.00
0.50
0.04
0.04
0.16
0.27
0.35
0.03±0.01
0.25(v12-v22)/2g
B-2
Appendix B
Hydraulic Reference Tables
PROPERTIES OF WATER
Specific Weight
Density
Dynamic
Viscosity
Kinematic
Viscosity
Vapor Pressure
Head
Temp
γ
ρ
μ
10-5 ν
Pv/γ
F
(lb/ft3)
(slug/ft3)
(lb∙sec/ft2)
(ft2/sec)
(ft)
32
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
212
62.42
62.43
62.41
62.37
62.3
62.22
62.11
62.00
61.86
61.71
61.55
61.38
61.20
61.00
60.80
60.58
60.36
60.12
59.83
1.940
1.940
1.940
1.938
1.936
1.934
1.931
1.927
1.923
1.918
1.913
1.908
1.902
1.896
1.890
1.883
1.876
1.868
1.860
3.746
3.229
2.735
2.359
2.05
1.799
1.595
1.424
1.284
1.168
1.069
0.981
0.905
0.838
0.78
0.726
0.678
0.637
0.593
1.931
1.664
1.41
1.217
1.059
0.93
0.826
0.739
0.667
0.609
0.558
0.514
0.476
0.442
0.413
0.385
0.362
0.341
0.319
0.2
0.28
0.41
0.59
0.84
1.17
1.61
2.19
2.95
3.91
5.13
6.67
8.58
10.95
13.83
17.33
21.55
26.59
33.9
ATMOSPHERIC PRESSURE
Elev
(ft)
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
(psi)
14.7
14.2
13.7
13.2
12.7
12.1
11.8
11.4
10.7
10.5
10.1
Water
Column
(ft)
33.9
32.7
31.6
30.4
29.4
28.2
27.2
26.3
24.8
24.2
23.4
Mercury Column
(in)
(mm)
29.92
760
28.9
734
27.87
708
26.81
681
25.9
658
24.92
633
24.01
610
23.19
589
21.89
556
21.39
543
20.63
524
B-3
Appendix B
Hydraulic Reference Tables
HYDRAULIC ELEMENTS CHART
1.00
0.90
Q/Qfull
A/Afull
0.80
V/Vfull
P/Pfull
0.70
d/D Ratio
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
Q/Qfull , A/Afull, V/Vfull, P/Pfull
B-4