CHAPTER

9

WATER

SUPPLY

Copyright© 2000. Delmar is a division of Thomson Learning.

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9

Objectives 1 of 3

• Explain the value of proper water supply.• Identify sources of water supply for drinking and

firefighting.• Explain the difference between ground water and

surface water.• Explain the purpose of mobile water supply apparatus.

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9

Objectives 2 of 3

• Explain the features of water distribution systems.• Identify types of fire hydrants and their uses.• Identify valves associated with water distribution

systems.• Explain how to operate a rural water supply.• Explain a portable water tank operation.• Explain tender operations.

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9

Objectives 3 of 3

• Identify the proper pressures associated with water distribution systems.

• Conduct a test of the operability and flow of fire hydrants.

• Determine the static, residual, and flow pressures of water sources.

• Identify the cause of obstructions and damage to fire hydrants and mains.

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9

Introduction 1 of 2

• Water supply is one of the most critical elements of firefighting.

• Water supply is important in areas with a water distribution system.

• Water supply even more important in areas without a water supply system.

• Firefighters must know how to establish a water supply.

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9

Introduction 2 of 2

• Water source, quantity, and how it is delivered are key questions.

• Fire flow capacity is dictated by the water supply.• Fire flow requirement is the amount of water required

for putting out the fire.• Water availability will dictate the strategy, tactics,

appliances, and fire streams used.

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9

Sources of Water Supply

• Need to know where water comes from and how it gets from that point to the fire scene.

• Many natural and man-made factors affect water sources.

• Weather is the greatest factor.• Some areas have abundant water supply while others

have none.

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9

Groundwater• Most of the earth’s freshwater supply is groundwater.• Groundwater usually results from rain.• Groundwater may collects in pockets called aquifers,

and rise as springs.• Water may reach surface through drilling and

pumping.• Water must have enough pressure for firefighting.

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9

Groundwater

Well pump with storage tanks.

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9

Surface Water

• Surface water is the world’s most common source.• Natural water sources used for firefighting are rivers,

lakes, and ponds.• Man-made sources include lakes, ponds, reservoirs,

swimming pools, and tanks.• Tidal changes may affect water sources.

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9

Surface Water

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9

Mobile Water Supply Apparatus

• Most engines today have at least a 500 gallon tank.

• Tenders have tanks from 1,000 to 8,000 gallons.

• Some tenders may have a pump.

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9

Tanks, Ponds, and Cisterns• Other developed sources are water tanks, ponds, and

cisterns.• Water tanks may be underground, ground level, or

elevated.• A cistern can hold large quantities of water (30,000

gallons or more.)• Connections for tanks or cisterns include dry hydrants,

drafting pits, or other type.

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9

Water Distribution Systems 1 of 2

• Include a method of getting water, treatment processes, storage, supply, and distribution.

• Water is supplied by three means:• Gravity fed.• Pumped system.• Combination pumped-gravity system.

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9

Water Distribution Systems 2 of 2

• After treatment, water goes into the distribution system.

• Water mains are divided into feeders.• Primary feeders divide into secondary feeders and

distribution lines.• Good systems are interconnected into loops and grids.

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9

Fire Hydrants

• There are two major types of hydrants:• Wet barrel.• Dry barrel.

• Dry hydrant is a piping system for drafting from a static water source.

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9

Wet Barrel Hydrant

• Have water in the barrel.• Used in non-freezing

temperature areas.• Each outlet controlled

by separate valve.

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9

Dry Barrel Hydrant

• Used in areas that have freezing temperatures.

• Valve at base of hydrant controls water flow to all outlets.

• Valve should be all the way open or all the way closed.

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9

Dry Hydrant

• Serves as connection point for drafting.

• A pipe system with a pumper suction at one end and a strainer at the other end.

• Used primarily in rural areas.

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9

Specialty Hydrants

• Wall hydrants mounted on side of building for direct connection to water supply system.

• Flush-type hydrants.• High-pressure hydrants.

CHAPTER

9Valves Associated with

Water Distribution Systems 1of 2

• Usually non-indicating type gate valves and check valves found in public water system.

• Gate valves are butterfly valves.• Check valves control water flow in one direction.• Backflow preventers are check valves or a pair of

check valves.

CHAPTER

9Valves Associated with Water

Distributions Systems 2 of 2

• Private water valves are of the indicating type such as:• Post indicator valve (PIV).• Wall indicator valve (WIV).• Outside stem and yoke (OS&Y).

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9

Rural Water Supply

• Rural water supply operation can occur anywhere.• Rural water supply should be understood by all.• Rural water supply operations require careful

coordination and control.• Water supply officer should be part of ICS.

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9

Portable Water Tanks

• Tenders are designed to transport water.• Must be able to quickly drop off water and return to the

fill site.• Each tender should have a portable water tank.• Tank usually set up next to attack or supply engine

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9

Portable Water Tank

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9

Tender Operations 1 of 3

• A tender operation is a shuttle operation.• Dump site is where water is delivered.• Site should be able to unload multiple tenders.• Site should have a turnaround area, operational area,

and access to fireground.• Site should allow for safety of personnel.

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Tender Operations 2 of 3

• Fill site should be properly staffed.• Shuttle operations control fire flow capacity.• Increased efficiency, more tenders, or larger tanks can

help increase flow rate.• Increasing vehicle speed will not speed up tender

operations.

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Tender Operations 3 of 3

Fire Flow Rate =

Time to fill tender +Time to drop water +

Travel time to and from dump site

Quantity of Water Carried

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9

CHAPTER

9Pressure Associated with Water

Distribution Systems 1 of 2

• All of the earth’s water is under pressure.• Seawater is under atmospheric pressure.• Drafting takes advantage of atmospheric pressure.• Pressure is the force, or weight, of water measured

over an area.• Pressure varies according to friction.

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9Pressure Associated with Water

Distribution Systems 2 of 2

• In the US, average water pressure is 65-80psi.• Pressure greater than 150psi can damage plumbing.• Recommended low residual pressure when pumping

from a hydrant is 20 psi.• Fire departments need to know pressures and capacities

of water distribution systems.

CHAPTER

9Testing Operability and

Flow of Hydrants 1 of 3

• Testing should be conducted periodically on fire hydrants.

• First tests involve operability of hydrant.• Remove all caps and check threads and gaskets for

damage.• Check that valves on the hydrant allow water to flow.

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9Testing Operability and

Flow of Hydrants 2 of 3

• Check drain valve on dry barrel hydrant • On a dry hydrant, visually inspect piping, caps and

gaskets.• Flow test and backflushing of hydrant are last parts of

testing dry hydrants.• Flow test should be conducted during normal

operations of water supply system.

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9Testing Operability and

Flow of Hydrants 3 of 3

• One flow test is a fireground method using gauges on the pumper.

• Other test is done during planning and requires a Bourdon gauge and Pitot gauges.

CHAPTER

9Determining Static, Residual,

and Flow Pressures 1 of 3

• Fireground flow testing involves connecting pumper to hydrant and turning it on.

• Static pressure is read on the main intake gauge prior to charging lines.

• Static pressure is the pressure without any water flowing.

• First line is then charged to desired volume.

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9Determining Static, Residual,

and Flow Pressures 2 of 3

• Once water is flowing, intake gauge is read to get residual pressure.

• Second test involves testing multiple hydrants. (Not conducted during fire operations.)

• First hydrant is used with the cap gauge to take a static pressure.

• Second hydrant is opened and flow measured with a Pitot gauge.

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9Determining Static, Residual,

and Flow Pressures 3 of 3

• Process continues until all hydrants are tested.• Next step involves calculation of discharges for

hydrants tested.• Formula used:

Q = 29.83 cd2 √P

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9

Gauges

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9Obstructions and Damage to Fire Hydrants and Mains

• Encrustrations and blockage of piping by minerals or organisms can restrict waterflow.

• Hydrants also subject to damage by vandals.• Damage from improper actions by firefighters may also

occur.• Failing to open or close valves fully or cross threading

connections results in damage.

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9

WRAP-UP 1 of 2

• Water is most common extinguishing agent.• Must understand relationship between water supplied

and amount needed.• Supplying water requires an understanding of the

components of a water distribution system.• Distribution systems have valves and hydrants to be

operated.

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9

WRAP-UP 2 of 2

• Firefighters must be able to use mobile supply apparatus, portable water tanks, and conduct shuttle operations.

• Firefighters need to be familiar with testing operability and the flow of hydrants.