1. Chapter 9
Water Supply

2. Introduction
Water supply is one of the most critical elements of firefighting
Water supply dictates the fire flow capacity
Pressure is the force of water
Measured over an area
Fire flow requirement is the amount of water required for putting out the fire
Water’s ability to absorb large quantity of heat makes it effective in fighting fire
Water cools the fuel below its ignition temperature

3. Sources of Water Supply
A wide range of natural and man-made factors affects water sources
Water in a constant cycle of change
Sun evaporates water into atmosphere
Condenses into clouds
Eventually falls as rain
Some areas alternate between rainy and dry seasons
Some areas have plenty of water, but it is frozen

4. Groundwater Most of Earth’s freshwater supply is groundwater
Seeps into the ground from rain and other sources
Collects in aquifers
Permeates into layers of water-bearing soil
Water table: level of water under Earth’s surface
Springs are groundwater sources that flow to the surface
Shallow wells prone to changes in water table
Deep wells more predictable
Less chance of contamination

5. Surface Water Almost 75 percent of the Earth covered with water
Most found in oceans and seas
Man-made surface sources include lakes, ponds, reservoirs, swimming pools, water tanks
Tidal changes are rising and falling of surface water levels
Due to gravitational effects between Earth and moon
May be as much as 40-foot difference between high and low

6. Mobile Water Supply Apparatus
Water tank on fire apparatus supplies the water
Small fires and fires in areas without water distribution system
Water tender: mobile water supply apparatus
Tenders combined with portable water tanks provide large volumes of water to fireground
Tenders may have small booster pump of at least 250 gpm
Fire pump of at least 750 gpm
Transfer pump of at least 250 gpm

7. Tanks, Ponds, and Cisterns
Water tanks may be:
Underground
Ground level
Elevated
May have a dry hydrant or other connection, or just a drafting point
Ponds may be developed for fire protection
Lined or unlined, with or without dry hydrants
Cistern: underground tank made from rock or concrete

8. Water Distribution Systems
Components of water distribution system:
Method of getting the water
Filtration, treatment processes
Storage, supply, and distribution
Small groundwater systems require a well with pumping station
Large well systems: multiple supply, processing, storage units with massive feeder lines
Water supplied in three ways: gravity fed, pumped, combination

9. (A)
(B)
(C)
Figure 9-4 (A) Gravity-fed water distribution system. (B) A direct pump water distribution system. (C) A combination gravity-pumped water distribution system.

10. Fire Hydrants Fire hydrants allow access to water supply systems
Two major hydrant types:
Wet and dry barrel hydrants
Dry hydrant: pipe system for drafting from static water source

11. Wet Barrel Water in the barrel up to valves of each outlet
Used in areas not subject to freezing
Allows each outlet to be controlled by separate valve
Additional lines taken off or supplied if outlet available
Additional connection does not require flow through other outlets to be stopped
Main control valve controls flow to all outlets

12. Figure 9-7 Typical schematic of wet barrel hydrant.

13. Dry Barrel
Used in areas where freezing temperatures could damage the hydrant
Valve at base controls water flow to all outlets
Base and valve below ground at water main
Entire hydrant shut down to connect additional lines
Operation in partially open position undermines the hydrant and ground
Imminent damage to roads and buildings

14. Figure 9-8 Dry barrel hydrant.

15. Figure 9-9 Typical schematic of dry barrel hydrant.

16. Dry Hydrant Not really a fire hydrant
Connection point for drafting from a static water source such as a pond or stream
Pipe system with pumper suction connection at one end and strainer at other
Primarily used in rural areas with no water distribution system
May be found in urban or suburban areas as backup water supply

17. Figure 9-11 Schematic of dry hydrant installation.

18. Specialty Hydrants Wall hydrants mounted on wall of a building
Be sure to connect to wall hydrant and not the fire pump test connection outlet
Direct connection to water supply system
Flush-type hydrant mounted below grade level
Found in a pit, vault, or valve box
Allows access to water source where above-grade hydrant interferes with operations
High-pressure hydrants connected to separate high-pressure water system

19. Figure 9-12 Wall fire hydrant.

20. Hydrant Protective Devices
Devices or valves designed to protect the water system
Most hydrants connected directly to domestic water supply
Many water suppliers added measures to protect water supply
Interior valves, exterior protective devices
Exterior systems require lock and key
Mostly found on privately owned property

21. Figure 9-13 External hydrant protective device.

22. Valves Associated with Water Distribution Systems
Gate valves (butterfly valves) opened and closed to control water flow
Nonindicating gate valves installed at:
Interconnections of water mains
Intermediate points of long sections of water mains
Before each hydrant and major building connection
Check valves control water flow in one direction
Backflow preventers: check valves that prevent backflow of water from one system into another

23. Figure 9-14 Hydrant with plumbing
Figure Hydrant with plumbing. Note the location of a gate valve between the water main and hydrant.

24. Rural Water Supply Rural water supply can occur anywhere
Urban and suburban areas often have places where hydrants are too far away
Limited access highways, large bridges
Require careful coordination and control
Water supply group supervisor part of incident command system
Full authority over water apparatus operations
Firefighters assigned to water supply are vital

25. Portable Water Tanks
Mobile water supply apparatuses must quickly offload water and return to fill site
Each mobile apparatus should have a portable water tank
Capacity equal or greater than its tank size
Collapsible or inflatable tanks set up next to engine
Jet dump speeds unloading of tanks
Multiple tanks using a jet siphon set up together

26. Figure 9-15 Portable water tanks are an essential piece of equipment for shuttle operations.
Figure Tender at dump site dropping water directly into portable tank.

27. Mobile Water Apparatus Operation
Shuttle operation involves moving water between dump site and fill site
Dump site: where water delivered for quick unloading
Set up first
Fill site: location of water source
Optimum fill site allows vehicles to drive through
Shuttle operations time cannot be decreased by increased vehicle speed

28. Pressure Associated with Water Distribution Systems
All Earth’s water under pressure
Atmospheric pressure: 14.7 pounds per square inch
Atmospheric pressure reduces 0.5 psi per 1,000 feet of elevation
Pressure in nonflowing closed system equal at all points
While flowing, reduced by friction and loss of pressure at opening

29. Pressure Associated with Water Distribution Systems (cont’d.)
Distribution systems supplied under pressure
System pressure never as high as firefighters prefer
Pressures below recommended low residual pressure create a vacuum in part of the supply
High-flow and/or high-pressure areas are an advantage
Low-flow and/or low-pressure areas should be avoided

30. Figure 9-21 Atmospheric pressure being exerted on container of water.

31. Figure 9-22 Pressure is expressed in pounds per unit area (psi).

32. Testing Operability and Flow of Hydrants
Regular testing identifies inadequate hydrants
Coordinated between fire and water departments
Operability testing:
Wet and dry hydrants:
Visual inspection for damage
Ensuring hydrant valve closed
Remove all caps, check threads and gaskets
Check that all valves allow water to flow

33. Testing Operability and Flow of Hydrants (cont’d.)
Operability testing (cont’d.):
Dry barrel hydrant:
Ensure drain valve working
Determine water level dropping after hydrant shut off
Visual inspection of piping, caps, gaskets
Flow test followed by backflushing of the hydrant
Replace caps, oil moving parts, and paint the hydrant
Fireground method for flow tests

34. Determining Static, Residual, and Flow Pressures
Connect a pumper to a hydrant and turn it on
Static pressure: pressure in the system with no hydrants or water flowing
Charge the first line with desired volume
Check compound gauge for residual pressure
Compare percentage of pressure drop from static to residual
Second test involves multiple hydrants
Not conducted during fire operations

35. Table 9-1 Percentage Drop Measurements

36. Obstructions and Damage to Fire Hydrants and Mains
Obstructions and damage can occur to fire hydrants and water mains
Small leaks develop as water system matures
Vandals damage by opening or closing valves
Opening valve in freezing weather without allowing water to flow may cause hydrant to freeze and crack
Accidents can crack pipes or break off a hydrant
Firefighters should ensure hydrant is opened or closed fully

37. Lessons Learned Water is the most common fire extinguishing agent
Must be supplied in sufficient quantity
Supplying water requires understanding of the water source and the valves and hydrants
In areas with no distribution system, create one
Difficult to sustain adequate fire flow with mobile apparatus