0. Fire Detection and Suppression
Chapter 3
Water Supply

1. 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)
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2. 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)
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3. 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, ,080) of heat if all the water is converted to steam.
(Continued)
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4. 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)
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5. 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.
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6. 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
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7. Water’s Disadvantages as an Extinguishing Agent
High surface tension
Reactivity
Low levels of opacity and reflectivity
Freezes at 32F (0C)
Conductivity
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8. 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)
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9. 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)
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10. 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)
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11. 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)
Water Supply

12. 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
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13. Pressure Loss and Gain Elevation Altitude
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)
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14. Friction Loss
That part of the total pressure lost while forcing water through pipe, fittings, fire hose, and adapters
(Continued)
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15. 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
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16. 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)
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17. 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
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18. 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
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19. Municipal Water Supply Systems
Components
Source of water supply
Means of moving water
Water processing or treatment facilities
Water distribution system, including storage
(Continued)
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20. 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)
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21. 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)
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22. Municipal Water Supply Systems (cont.)
Water Distribution System
Dead-end hydrants
Circulating feed or looped lines
Grid system
Primary feeders
Secondary feeders
Distributors
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23. 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)
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24. 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)
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25. Water Distribution System Variables
Piping arrangement (cont.)
Valves
Function in system
Location in system
Access
Indicating
Nonindicating
Gate valves
Butterfly valves
(Continued)
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26. Water Distribution System Variables
Piping arrangement (cont.)
Hydrants
Dry-barrel and wet-barrel
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27. 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
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28. 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)
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29. 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)
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30. 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)
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31. Private Water Supply Systems
Water supply requirements for automatic sprinkler systems (cont.)
Duration of water supplies
See Table 3.5 in manual
NFPA 231, Standard for General Storage
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