ME31B: CHAPTER SEVEN
DESIGN OF EXTERNAL
FACILITIES ONE
INTRODUCTION

This chapter deals with structures
which are only indirectly related to
buildings, but which are of great
importance to the farmer.

These include: roads, culverts, bridges
and water distribution systems related
to farming activities.
7.1 INTRODUCTION TO SIMPLE
ROAD DESIGNS



Rural access roads range from the simplest
earth roads to bituminous surfaced
highways. However, earth roads are normally
the only type that can be justified for access
to farmsteads.
These roads, designated as unimproved
earth roads, are generally suitable solely for
light traffic, up to some dozen or so vehicles
per day, and they often become impassable
in the wet season.
Heavy lorries, which sometimes need to have
access to farmsteads, should only be allowed on this
type of road after an adequately long dry spell.
Simple Roads Contd.

There is no need for actual structural
design of unimproved roads, but there
are some principles, which if followed,
will produce a reasonably good road for
the small investment that they justify.
7.1 Road Location



A survey to determine the best location for a
road line starts by identifying areas through
which the road must pass, for example:
A gap between hills, the best location for a
river crossing, and points to be linked by the
road.
Places to be avoided include soft ground,
steep slopes, and big rocks. In large scale
road projects the terrain is viewed from aerial
photographs, but for smaller projects this is
too costly and instead an overview of the
proposed road line must be obtained from
adjacent hills.
Road Location Contd.

Such an overview provides valuable
information on natural drainage, but
should always be supplemented by a
detailed examination on foot.

Once the points through which the road
must pass have been established, the
road line is laid out to run as directly as
possible between them
Road Gradients



A steep gradient not only slows down traffic
and limits the load a draught animal can pull,
The recommended gradient standards for
unimproved roads differ in different
countries, but generally, for roads used
mainly by motor vehicles, the gradient should
not exceed 1 in 17 in flat or rolling terrain, 1
in 13 in hilly terrain, or 1 in 11 in
mountainous terrain.
In exceptional cases it may be necessary to
have steeper gradients, but their maximum
length should then be limited.
Road Curves


A straight road is the shortest distance
between two points, but this may not be the
most economical line for a durable, easily
constructed road which is passable
throughout the year.
Long gentle curves are preferred since there
is better visibility and less speed reduction
necessary than on a sharp corner. The
minimum radius for a horizontal curve is 15m
but 30m or more is preferable.
Road Slopes


Only occasionally will an unimproved
road require embankments or cuttings,
but where it cannot be avoided, the
side slopes should not exceed 1 in 1 on
well-drained soils. In wet soil it should
not exceed 1 in 3, i.e. one unit rise in
three units of horizontal distance.
These are maximum values and should
only be used where the depth of the cut
or fill is so large that to reduce the
slope would be too expensive.
Road Camber


The camber is the slope of the road surface
to the sides designed to shed water into the
side drains.
A simple earth track has no camber and no
side drains. But all other roads should have a
camber of 5 to 7% from the middle of the
road, thus shedding water into both side
drains. In deep cuts (where the road is dug
into a hill side) or on sharp curves, the
camber is designed to drain water from the
whole surface inwards toward the cut or to
the inside of the curve.
7.1.6
Cross Section of a Simple
Earth Track



The simplest earth track is obtained by
merely clearing vegetation and stones from
the natural soil surface.
It may run between fields within a farm, from
the main road to a farmstead or between
small villages where the traffic volume is very
low.
Earth tracks are based on single lane traffic
in one pair of wheel tracks, but vegetation
should have been cleared wide enough to
allow for two small cars to meet.
Cross-Section of a Simple Earth
Track
Cross Section of an Upgraded
Earth Road
These roads may be used to connect rural
market centres and villages where the traffic
volume is 10 to 20 vehicles per day including
some heavy lorries in the dry season.
Generally the only affordable surface material
is the soil found on the line of the road or in
its immediate surroundings.
The bearing capacity of the road depends on
the type of soil and the prevailing climatic
conditions.
Cross Section of an Upgraded
Earth Road Contd.
The road is constructed by digging out
soil from the sides and throwing it on
the road until the cross section
illustrated in Figure below is obtained.
The 30 cm difference in level between
the road surface and the bottom of the
side drains, combined with the camber
of the road surface, will ensure a much
drier roadway with higher carrying
capacity than the simple earth track.
Methods For Improving Earth Roads





Gravelling – Reduces the risk of mud
forming
Paving with pit run or with pitch
Grassing to improve their strengths
Constructing side drains
These improvements are common on earth
roads in Trinidad including Nariva Swamp
7.1.8




Road Construction
When the land has been surveyed and the
most feasible road line has been found, the
centre line of the road is set out with pegs
inserted at 15 to 20m intervals and tall
enough to be clearly visible.
Additional pegs may be installed to mark the
width of the roadway, side drains and the
area to be cleared.
Stumping and Clearing
To construct a simple earth road, trees and
rocks must be cleared from the road line and
well back from the road so that sun and wind
can dry the road surface.
Road Construction Contd.





If the objective is to construct a high-level
earth road, the work will continue with the
construction of side drains.
Construction of Side Drains
Using wooden pegs and string as a
guideline, the edge of the road should be
established 1.8 to 2.0m from the center line.
On roads with no cross-fall, side drains are
dug out of either side to a depth of 150 mm
and half the width of the roadway.
All soil thus dug out is thrown on to the road
and spread to form an even road surface
with correct camber.
7.1.8



Road Maintenance
The most important maintenance job on any
type of earth road is to ensure that all drains
work properly and that additional drains are
installed wherever it becomes necessary.
Secondly, rutted wheel tracks should be filled
in with soil from outside the road bed.
If the road surface becomes badly
deteriorated it will be necessary to resurface
the road by adding more soil from the side
drains.
7.1
Culverts

Where the road crosses a natural water
way, a culvert or bridge should be built.

Culverts are best suited for streams
with
steep
banks,
since
their
construction requires some difference
in height between the level of the road
surface and the bed of the stream.
Culverts Contd.





Culvert construction consists of the following:
1 The actual culvert (one or more pipes),
which carries the water under the road.
2 The embankment, which carries the road
across the water course.
3 Wing walls, which protect the embankment
from flood water and direct the flow into the
culvert.
4 The apron at the discharge end, which
prevents erosion of the stream bed.
Culverts Contd.




The normal water flow is carried by the
culvert, but large flows of storm water are
allowed to flow over the top of the
embankment.
Concrete pipes, 400 to 900 mm in diameter,
are often used for culverts.
The diameter and number of pipes is
determined by the expected water flow.
Alternatively corrugated steel pipes or
masonry work in burnt bricks, concrete
blocks or stone may form the culvert.
Culverts Concluded


Where concrete pipes have been used for a
culvert, the embankment must provide for a
soil cover above the pipe to a depth at least
equal to the diameter of the pipe in order to
sufficiently protect the pipes from the load of
heavy vehicles.
The beams in the ceiling of a square shaped
culvert with masonry walls may be designed
to carry the load of vehicles, thus reducing
the need to spread the load in the
embankment by a soil cover.
7.1 Simple Bridges



The ideal site for a bridge is where the
river is narrow and the banks are solid.
The bridge should be designed to
interfere as little as possible with the
natural flow of water.
The highest level, which the river is
known to have reached, is determined
and the bridge designed to give at least
0.5m clearance above that level.
Components of Simple Bridges



1. Abutments, the structures provided to
strengthen the stream banks and adequately
support the shore end of the road-bearing
beams.
They can be constructed of concrete,
masonry work (stone, brick, concrete blocks)
or timber. The lower part of the abutments
will normally require wing walls to protect
them from the action of the stream.
Intermediate supports installed where the
stream is too wide to be bridged in a single
span. Timber trestles, masonry piers and
reinforced concrete columns are the most
common types of support.
Components of Simple Bridges Contd.



2. Road-bearing beams that carry the
weight of the roadway and traffic between
abutments and any intermediate supports.
Simple bridges have road-bearing beams
consisting of round or sawn timber or
universal steel beams spaced about 600 mm
center-to-center across the roadway.
For example, a bridge 3.0m wide requires 6
beams and a bridge 3.6m wide, 7 beams etc.
The beams are usually designed as simple
beams supported at the ends.
Components of Simple Bridges Contd.



3. Decking or flooring, which make up the
road surface on the bridge.
Where poles or other rough materials have
been used for decking a smoother surface
can be obtained by putting planks along the
bridge for the wheel tracks.
The decking should be strong enough to
spread the load from one wheel over at least
two road-bearing beams. Wooden decking
should never be covered with soil, since that
will increase decay and disguise any
weakness in the bridge.
Components of Simple Bridges
Concluded


4. Curbs made from poles or pieces of
timber should be secured to the edges
of the decking. Curbs will reduce the
risk of vehicles slipping over the edge
and will also, if positioned over the
outer road-bearing beams and well
secured to them, contribute to the
strength of the bridge.
5. Rails along the edges of the bridge
for safety.
Concluding Remarks About Simple
Bridges



The bridge must be designed to carry the
weight of the members of the bridge (dead
load) and the weight of any traffic moving
across it (moving load).
In order to simplify calculations, the moving
load is often converted to an equivalent live
load by multiplying it by 2.
When a heavy lorry moves across the
bridge, the bridge will carry concentrated
loads from the wheels with spacing equal to
the wheelbase and tread-width.
Concluding Remarks About Simple
Bridges Contd.


In a bridge of short span the largest bending
moment in the road-bearing beams will occur
when the back wheels which carry the
greatest weight are at the centre of the span
and will be determined by half the weight on
one wheel, since the decking is designed to
distribute the load to at least two beams.
In a bridge of longer span where both front
and rear wheels may be on the span at the
same time, the maximum bending moment
will occur when the centre of the wheel base
is a short distance from the centre of the
span.
Concluding Remarks About Simple
Bridges


In addition to bending, shear may have
to be considered in short spans, and
deflection for long spans.
Where bridges are constructed with
rough materials under unfavourable
conditions, a larger factor of safety
should be used.
7.1 DESIGN OF WATER
DISTRIBUTION SYSTEMS



7.4.1 Demand and Consumption of
Water:
Consumption is the amount of water
used in reality e.g. in domestic needs.
It rises to demand according to water
supply improvements.
Demand is the amount of water that
would be used by consumers if
available, under specific conditions of
price, quality and others.
Uses of Water

Water is normally used for domestic,
tourist,
fire-fighting,
industrial,
agricultural (mainly irrigation) and
hydro-electricity.

Typical domestic water use in the
Caribbean is given in Table 7.1 below.
Table 7.1: Domestic Water Use in Selected Countries in the
Caribbean
Country
Water Use
(Litres/per capita/d)
Barbados
217
Belize
109
Dominica
210
Grenada
114
Guyana
A1
A2
A3
270
135
90
St. Lucia
160
Suriname
127
Trinidad & Tobago
A1
A2
A3
297
160
126
A1 - Houses with direct house connections and Internal Plumbing
A2 - Houses served at a point
A3 - Houses with access to public stand pipes
Source: UWI Infrastructure for Development (1996)
Agricultural Water Use


The agricultural consumption is mainly
the crop water requirements, usually
higher than human needs.
In the
Caribbean region, this ranges from 1 to
1.5 m (gross) per crop per season.
This amounts to about 10 to 15 million
litres per crop per season.
Another
form
of
agricultural
consumption is livestock requirement,
which can be about 64 litres per hr per
day for cattle.
Water Contd.

Design should be based not on present
water demand but on future demand
estimation which is normally obtained
by extrapolation.
7.1.1
Peak Factors
Water design should not only provide the mean water requirement
but also for the peak requirements in the year.
Peak Day Factor 
Peak Day ' s Use
.
Mean daily Use
A typical range of values of peak factor for the developing countries is 1.1
to 1.3
Also variation in water demand is more during the day than from
day to day. Figure 7.5 below shows that water use varies at different hours
throughout the day.
12a.m.
4a.m. 8a.m. Noon 4 p.m. 8 p.m. Midnight
Figure 7.5: Typical daily cycles in Water Demand
Peak Hour Factor 
Water Consumption in Peak Hour
Average Water Consumption
Typical values for rural communities in developing countries is up to 2 and can go
up
to 3 in developed countries and 4 to 4.5 in individual farms.
Water Source
Peak day (small pipes)
(1.1 – 1.3)
WATER
STORAGE
Point of Use
Peak hour (larger pipes)
( 2 – 4)
A day’s peak consumption is needed in storage to meet the demand of peak water
use. Small pipes are needed to convey water from source to storage while bigger ones
convey it from storage to points of use.
7.4.2 Storage and Distribution
of Water






Service Reservoirs: Storage in water
supply network
7.4.3.1 Purposes for Storage
(i) To balance supply and demand
(ii)Protection against breakdown
(iii)
To provide a static head for
gravity running
(iv)
Water treatment.
Siting and Capacity of Reservoir


7.4.3.2 Siting of Reservoir: It should be
sited as close as possible to point of use
within constraints of available relief. This is
to reduce the pipe cost due to the higher
discharge from storage to points of use.
7.4.3.3 Capacity of Reservoir:
Inflows
should be kept fairly even. Outflows can be
peaked. Storage is used to balance uniform
inflow and non-uniform outflows. If inflow is
greater than outflow, then water is getting
into storage and if outflows is greater than
inflows, water is coming out of storage.
7.4.3.4 Pipes




There are three categories of pipes:
(i)Mains:Trunk
- not tapped and
Distribution Mains – supply water. They
have relatively large diameter and are used
for conveyance and distribution. Materials
used include cast iron, spun iron, asbestos,
cement, or steel.
(ii) Service Pipes: Individual supply lines to
farms, houses and hospitals or standpipes.
Materials used include
copper, steel,
plastics (PVC or polyethylene).
(iii)
Plumbing:
Pipe work within the
building
7.4.3.4 Pressure Classes of Pipes




There are three important pressures
associated with pipes.
(i) Work Test: 2 to 3 times the working
pressure. It is the pressure used to test
manufactured pipes.
(ii) Maximum Field Test: One and half
times the working pressure. The specified
design pressure should be tested in the field.
(iii)
Maximum
Working
Pressure:
Maximum pressure derived in the field.
There are three classes of maximum working
pressures e.g. polyethylene Class B- 6 bars,
Class C - 9 bars and Class D – 12 bars.
7.4.3.4 Pipeline Design

The selection of pipes is an economic
tradeoff between large diameter which will
give high capital cost and low friction losses
and low pumping costs (if there is pumping)
OR small diameter, which will involve low
capital cost, more head losses and more
pumping cost.

Energy cost is a function of head losses
while pipe cost is a function of diameter.
Allowable Head Losses




(i) Allow 1 m (for big pipes) to 10 m (small
pipes) head loss per 1000 m of mainline
(ii) Using velocity as criteria as head loss
effects is related to velocity.
Normal practice in water supply for irrigation
is to keep velocity within 0.6 to 1.5 m/s.
Above that, there can be ‘water hammer’ or
high rates of corrosion. Water hammer is
transient high pressure waves due to rapid
valve closure. Below 0.6 m/s, there may be
silting or sediment deposition.
Pipe diameter can be chosen using head
losses and velocity using charts or
equations.
7.4.3.4 Pipe Layout: Types of
Distribution Systems

(i)Individual Pipes: Connects
two points in the distribution
system say from a reservoir to
the point of use.
Example 1: A reservoir (Figure 7.7) is situated 65 m vertically
above some farm buildings. The length of pipe required to lead
water from the reservoir is 750 m and the pressure required at the
buildings is 30 m head. Rate of flow required is 2 m3/h (2000
litre/hr).
Solution:





If the head available due to the height of the
reservoir is 65 m, and the pressure head
needed at the buildings is 30 m, the head
available for overcoming friction is 65 – 30 =
35 m being the difference in head between
the ends of the pipe.
The equivalent length of the pipe is:
Actual length (750 m) + 10% (75 m)
= 825 m
Plus (say) 1 tap + 2 stop taps = 135 m
Total = 1060 m
Solution Concluded



The hydraulic
gradient is Pressure
difference/ equivalent length = 35/1060 =
1/30
Since the maximum head is 65 m, a Class C
(9 bar or 90 m) pipe is required, and referring
to Chart provided, it can be seen that a 32
mm nominal (internal) diameter Class C low
density polythene pipe would satisfy these
requirements.
Velocity is about 0.8 m/s which is acceptable
(within 0.6 and 1.5 m/s).
Chart
(ii) Branching System





The advantages are relatively few joints and
the system is easy to build and design.
The disadvantages are that sediments may
accumulate at dead ends of the pipe.
Secondly, it there is pipe bursts, a total cut
off for zone beyond failure results.
This means that in case of bursts, the
system will be cut off.
Also there is limitations in adding to the
system beyond a certain point.
Because of these disadvantages, branch
system is used in small community projects.
Example 2: For the branching pipe system shown below: At B and C, a
minimum pressure of 5 m. At A, maximum pressure required is 46 m and the
minimum is 36 m. Select a suitable diameter for AB and BC.
0.15 l/s
219 m A
2.9 m3/h
700m
2.4 m3/h
0.5m 3/h
825 m
B 189 m
Public water main
C (219 m,
Solution: Computation Table
Pipe Flow Leng Pipe Head Flow Head Elev. Grou Press Rem
nd
Head .
Sect. (m3/ th
Dia Loss Vel Loss of
h)
(m) mm (m/1 m/s (m) hydr. level (m)
00 m
Grad elev
e (m) (m)
23
A
260
B
237
189 46
O.K
BC 0.5 825 19 1.6 0.5 13
B
237
C
224
219 5
Just
O.K
AB 2.9 700 32 3.3
0.85
Explanation of Table




The average of the maximum and minimum
pressure required at A is 41 m.
If you subtract the minimum pressure
needed at B (5 m) from 41 m, you get 36 m.
Since the length of the pipe is 700 m, the
hydraulic head loss is 36/700 = 0.051 =
5/100 = 1/20.
With the discharge of 2.9 m3/h and head loss
of 1/20, the next higher diameter of pipe is
32 mm from the chart.
Chart
Explanation of Table Contd.



With now 32 mm diameter pipe chosen in
column 4 of the Table, and the same flow
rate, the actual head loss is now 1/30 from
the chart which is 3.3 m/100m as shown in
column 5.
The flow velocity is about 0.85 m/s which is
acceptable.
The head loss is now (3.3 x 700)/100 = 23
m. At A, the elevation of the hydraulic grade
line is now 41m + ground elevation (219 m) =
260 m.
Explanation of Table Contd.




For B, it is 260 minus the head loss (23 m)
which is 237 m.
The ground elevation at B is 189, so the
pressure head of water is 237 – 189 = 48 m
which is adequate.
For Pipe BC, the design flow is 0.5 m3/h.
The hydraulic grade line at B is still 237 m
and the elevation at C is 219 m.
The hydraulic grade line required at C is 219
m plus 5 m head of water, making a total of
224 m.
Explanation of Table Concluded.





The hydraulic gradient from B to C is then
(237 – 224)/825 = 0.016 which is 1.6/100 =
1/60.
With hydraulic gradient = 1/60 and the flow
rate of 0.5 m3/s, the diameter of pipe from
the Chart is exactly 19 mm.
The velocity is 0.5 m/s which is barely
acceptable.
The head loss is 0.016 x 825 m = 13 m.
The hydraulic grade line at C is therefore 237
m – 13 m, which is 224 m. This will give the
pressure head of 5 m required at C.
(iii)Grid Pattern/Looped Network




Interconnected pipes – water reaches a point
from a number of directions.
The advantages are that there will be no
stagnation i.e. no dead ends and during
repairs (pipe burst), there will be no need for
complete cutoff.
Only some parts of the system will be cut off.
There are also more even pressures
throughout the system.
The disadvantages are that the designs are
more complicated and there are more pipes
and more fittings.
Pipe Network Analysis Using the
Hardy Cross method.

The Hardy Cross system is used for
water flow analysis in a more complex
system than the dead end system.

There are two principles:
closed loop:
In any
7
(i) Flow into a junction is equal to the flow out of it. That is allowing for signs:
Q  0
(ii)
(ii) The algebraic sum of pressure losses round a circuit must be zero. That is
allowing for signs:
h
f
0
Q1
Q2
3
1
4
Q3
2
Q4
According to first principle: Q1 + (-Q2) + (-Q3) = 0
Also: Q2 + Q3 + (-Q4) = 0
For the second principle: hf (1) + hf (2) + hf (3) + hf (4) = 0
Convention: Positive sign is given to clockwise flow and negative sign is given
to anticlockwise flow.
Procedure For Analysis




1. Assign assumed flows to each pipe
segment in network such that at each
junction:
2. Calculate hf for each pipe using for
example Hazen Williams equation:
hf = 10.67 CH -1.85 D- 4.87 Q1.85 L
Where hf is head loss (m), CH is roughness
coefficient of pipe material ; D is diameter of
pipe (m), Q is water flow rate (m3/s) and L is
length of pipe (m).
Divide up network into closed loops such that each pipe occurs at least once.
 h with due regard for sign.
More than likely,  h will not be zero.
For each circuit, determine
be zero.
Compute
f
f
hf
Q
for each circuit. Disregard the sign.
Using that get the correction factor:
 h f
Q 
h
m f
Q
Correct the flows estimated in stage 1 as follows:
Qnew  Qold  Q
with due regard to signs.
Remember that
h
f
mu
Procedure Concluded

For any pipe that occurs twice, do the
correction for the two loops.
B
E
C
 BC occurs twice.
F
A
D

8. Repeat from step 2 until desired accuracy
is obtained.
Example
Example: Obtain the flow rates in the network shown below.
90 l/s
A
55
600 m
B
45
254 mm
10
35
600 m
152 mm
600 m
254 mm
C
+ve
600
152 mm
C
15
15
60l/s
66600
E
600 m
152 mm
5
D
600 m
152 mm
Solution



ABDE is one loop as shown above and
BCD is the second loop.
Note that the clockwise water flows are
positive while the anti-clockwise ones
are negative.
Positive and negative flows give rise to
positive and negative head losses
respectively
Solution
Circuit
I
Pipe
L (m)
D (m)
Q (m3/s)
hf (m)
hf/Q
AB
600
0.254
+ 0.055
2.72
49.45
BD
600
0.152
+ 0.01
1.42
142
DE
600
0.152
- 0.005
- 0.39
78
EA
600
0.152
- 0.035
-14.42
412
- 10.67
681.45
Total
II
BC
600
0.254
+ 0.045
1.88
41.8
CD
600
0.152
- 0.015
- 3.01
200.67
DB
600
0.152
- 0.010
- 1.42
142
- 2.55
384.47
Total
Sample Calculation: Using the Hazen Williams Equation in Step 2 :
hf for pipe AB = 10.67 x 135 – 1.85 x 0.254
-4.87
x 0.055 1.85 x 600 = 2.72
Q
0.008
0.004
 h f
10.67
Q1 

 0.00846  8l / s
h f 185
. x 68145
.
m
Q
2.55
Q2 
 0.00359  4l / s
185
. x 384.47
Correct the flows as shown below:
90 l/s
A
63
B
49
27
C
14
60 //s
11
E
30 l/s
3
D
Circuit
I
Pipe
L (m)
D (m)
Q (m3/s)
hf (m)
hf/Q
AB
600
0.254
+ 0.063
3.5
55.5
BD
600
0.152
+ 0.014
2.67
190.71
DE
600
0.152
+ 0.003
0.153
51
EA
600
0.152
- 0.027
- 8.92
330.37
- 2.6
681.45
Total
II
BC
600
0.254
+ 0.049
2.2
44.9
CD
600
0.152
- 0.011
- 1.69
153.64
DB
600
0.152
- 0.014
- 2.67
190.7
- 2.55
389.25
Total
 h f
2.6

 0.002  2 L / s
hf
185
. x 627.58
m
Q
2.16
Q2 
 0.003  3 L / s
185
. x 389.25
Q1 
Q
0.002
0.003
Correct flows again for the third trial
90 l/s
65
A
B
52
25
13
C
60 l/s
8
E
30 l/s
5
D
Circuit
I
Pipe
L (m)
D (m)
Q (m3/s)
hf (m)
hf/Q
AB
600
0.254
+ 0.065
3.72
57.2
BD
600
0.152
+ 0.013
2.31
177.7
DE
600
0.152
+ 0.005
0.39
78
EA
600
0.152
- 0.025
- 7.7
308
- 1.28
620.9
Total
II
BC
600
0.254
+ 0.052
2.46
44.9
CD
600
0.152
- 0.008
- 0.94
153.64
DB
600
0.152
- 0.013
- 2.31
190.7
- 0.79
342.5
Total
 h f
128
.

 0.001  1 l / s
h f 185
. x 620.9
m
Q
0.79
Q2 
 0.00125  1 l / s
185
. x 342.5
Q1 
Q
0.001
0.003
Final Water Flows
Final Water Flows
90 l/s
66 l/s
53 l/s
24 l/s
13 l/s
60 l/s
7
30 l/s
6 l/s
Note: A computer programme exists for analysis using the Hardy Cross Method