Fire Detection and
Suppression
Chapter 3
Water Supply
Characteristics of Water
• Compound of two parts hydrogen and one part
oxygen (H20)
— Liquid between 32F and 212F (0C and 100C)
— Solid below 32°F (0C)
— Gas above 212°F (100°C)
• Incompressible
• Weight for fire protection purposes=62.5 lb/ft3
or 8.33 lb/gal (1 kg/L)
3-1
Water Supply
Extinguishing Properties
of Water
• The law of specific heat: the specific heat of
any substance is the ratio between the
amount of heat needed to raise the
temperature of a specified quantity of a
material and the amount of heat needed to
raise the temperature of an identical quantity
of water by the same number of degrees.
(Continued)
3-2
Water Supply
Extinguishing Properties
of Water (cont.)
• The law of latent heat of vaporization
— The latent heat of vaporization is the quantity of
heat absorbed by a substance when it changes
from a liquid to a vapor.
— 1 gallon of water will absorb 9,346 Btu (1,266 +
8,080) of heat if all the water is converted to
steam.
(Continued)
3-3
Water Supply
Extinguishing Properties
of Water (cont.)
• Surface area of water: the speed with which
water absorbs heat increases in proportion to
the water surface exposed to the heat.
— Expansion ability
— Smothering ability
(Continued)
3-4
Water Supply
Extinguishing Properties
of Water (cont.)
• Specific gravity: the density of liquids in
relation to water
— Liquids with a specific gravity less than 1 are
lighter than water and therefore float on water.
— Most flammable liquids have a specific gravity of
less than 1.
3-5
Water Supply
Water’s Advantages as an
Extinguishing Agent
• Greater heat-absorbing capacity
• Large amount of heat required to change
water into steam
• Easily expanded surface area
• Plentiful supply
3-6
Water Supply
Water’s Disadvantages as
an Extinguishing Agent
• High surface tension
• Reactivity
• Low levels of opacity and reflectivity
• Freezes at 32F (0C)
• Conductivity
3-7
Water Supply
Water Pressure and Velocity
• Pressure: force per unit area on a liquid or
gas expressed in psi or kPa
• Force: simple measure of weight
• Velocity
— The speed at which fluid travels through hose or
pipe
— Result of pressure exerted on the fluid at its
source
(Continued)
3-8
Water Supply
Water Pressure and Velocity
(cont.)
• Principles of pressure
— First Principle: fluid pressure is perpendicular to
any surface on which it acts.
— Second Principle: fluid pressure at a point in a
fluid at rest is the same intensity in all directions.
— Third Principle: pressure applied to a confined
fluid from without is transmitted equally in all
directions.
(Continued)
3-9
Water Supply
Water Pressure and Velocity
(cont.)
• Principles of pressure
— Fourth Principle: the pressure of a liquid in an
open vessel is proportional to its depth.
— Fifth Principle: the pressure of a liquid in an open
vessel is proportional to the density of the liquid.
— Sixth Principle: the pressure of a liquid on the
bottom of a vessel is independent of the shape of
the vessel.
(Continued)
3-10
Water Supply
Water Pressure and Velocity
(cont.)
• Types of pressure
— Atmospheric pressure: pressure exerted on the
earth by the atmosphere itself
— Head pressure
–
–
Height that a pressure can lift a column of liquid
Height of a water supply above the discharge orifice is called
the elevation head.
— Static pressure: stored potential energy available
to force water through pipe, fittings, fire hose,
and adapters
(Continued)
3-11
Water Supply
Water Pressure and Velocity
• Types of pressure (cont.)
— Normal operating pressure: pressure found in a
water distribution system during normal
consumption demands
— Residual pressure: that part of the total available
pressure not used to overcome friction loss or
gravity while forcing water through pipe, fittings,
fire hose, and adapters
— Flow pressure (velocity pressure): forward
velocity pressure while water is flowing
3-12
Water Supply
Pressure Loss and Gain
• Elevation
— Center line of the pump or the bottom of a static
water supply source above or below ground level
— Elevation pressure results from differences in
elevation of nozzle and pump.
• Altitude
— Position of an object above or below sea level
— Effects of lower atmospheric pressure on drafting
above 2000 feet (600 m)
3-13
Water Supply
Friction Loss
• That part of the total pressure lost while
forcing water through pipe, fittings, fire hose,
and adapters
(Continued)
3-14
Water Supply
Friction Loss (cont.)
• Causes
— Movement of water molecules against each other
— Linings in fire hose/inside surface of piping
— Hose couplings/pipe fittings
— Sharp bends
— Change in hose size or in orifice by adapters
— Improper hose-coupling gasket size/pipe control
valves
3-15
Water Supply
Friction Loss (cont.)
• Principles of friction loss:
— First principle: if all other conditions are the same, friction
loss varies directly with the length of the hose or pipe.
— Second principle: when hoses are the same size, friction
loss varies approximately with the square of the increase in
the velocity of the flow.
— Third principle: for the same discharge, friction loss varies
inversely as the fifth power of the diameter of the hose.
(Continued)
3-16
Water Supply
Friction Loss
• Principles of friction loss (cont.):
— Fourth principle: for a given flow velocity, friction
loss is approximately the same, regardless of the
pressure on the water.
• Other factors affecting friction loss: diameter
and length of hose or pipe
• Reducing friction loss
3-17
Water Supply
Water Hammer
• Energy surge that results from suddenly
stopping or starting water moving through
hose or pipe
• Can damage the pump, appliances, hose, or
the municipal water system itself
3-18
Water Supply
Municipal Water
Supply Systems
• Components
— Source of water supply
— Means of moving water
— Water processing or treatment facilities
— Water distribution system, including storage
(Continued)
3-19
Water Supply
Municipal Water
Supply Systems (cont.)
• Sources of water supply
— Public water supply system
— Surface or ground water
• Means of moving water
— Directing pumping system
— Gravity system
— Combination system
(Continued)
3-20
Water Supply
Municipal Water
Supply Systems (cont.)
• Water processing or treatment facilities
— The fire department’s main concern regarding
treatment facilities is that a maintenance error,
natural disaster, loss of power supply, or fire
could drastically reduce the volume and pressure
of water available for fire fighting operations.
(Continued)
3-21
Water Supply
Municipal Water
Supply Systems (cont.)
• Water Distribution System
— Dead-end hydrants
— Circulating feed or looped lines
— Grid system
3-22
–
Primary feeders
–
Secondary feeders
–
Distributors
Water Supply
Water Distribution
System Variables
• Piping materials
• Pipe diameter
• Piping arrangement
— Simple loop
–
One inflow point and one outflow point.
–
Exactly two paths between the inflow and outflow
points.
(Continued)
3-23
Water Supply
Water Distribution
System Variables
• Piping arrangement (cont.)
— Complex loop (grid)
–
More than one inflow point
– More than one outflow point
–
More than two paths between inflow and outflow
points
(Continued)
3-24
Water Supply
Water Distribution
System Variables
• Piping arrangement (cont.)
— Valves
–
–
–
–
–
–
–
Function in system
Location in system
Access
Indicating
Nonindicating
Gate valves
Butterfly valves
(Continued)
3-25
Water Supply
Water Distribution
System Variables
• Piping arrangement (cont.)
— Hydrants
–
3-26
Dry-barrel
and
wet-barrel
Water Supply
Water Distribution
System Variables
• Piping arrangement (cont.)
–
Distribution and location
–
Maintenance
–
Color coding:
Less than 500 gpm: Red
500999 gpm :
Orange
1,0001,499 gpm:
Green
1,500 gpm or more: Light Blue
3-27
Water Supply
Private Water Supply
Systems
• Purposes
— To provide water strictly for fire protection
purposes
— To provide water for sanitary and fire protection
purposes
— To provide water for fire protection and
manufacturing processes
• Potential problems for fire fighting purposes
(Continued)
3-28
Water Supply
Private Water Supply
Systems (cont.)
• Water supply requirements for standpipe and
hose systems
— NFPA 14, Standard for the Installation of
Standpipe and Hose Systems
— Class I service
— Class II service
— Class III service
(Continued)
3-29
Water Supply
Private Water Supply
Systems (cont.)
• Water supply requirements for automatic
sprinkler systems
— NFPA 13, Standard for the Installation of
Sprinkler Systems
— Pipe schedule systems
— Hydraulically designed water-based
extinguishing systems
(Continued)
3-30
Water Supply
Private Water Supply
Systems
• Water supply requirements for automatic
sprinkler systems (cont.)
— Duration of water supplies
– See Table 3.5 in manual
–
3-31
NFPA 231, Standard for General Storage
Water Supply