Essentials of Fire Fighting, 5th Edition

Chapter 12 — Water Supply

Firefighter II

Firefighter II12–2

Chapter 12 Lesson Goal

• After completing this lesson, the student shall be able to choose the correct water supply for various scenarios and be able to move water through a system correctly.

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Specific Objectives

1.List sources of water supply. 2.Describe the three methods of moving water in a system. 3.Discuss water treatment facilities.

(Continued)

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Specific Objectives

4.Explain the operation of water storage and distribution systems. 5.Distinguish among the pressure measurements relevant to water supply. 6.Use a pitot tube. (Skill Sheet 12-II-1)

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Surface Water Supply

• Rivers• Aqueducts• Lakes• Reservoirs

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Groundwater Supply

• Water wells drilled into underground aquifers

• Water-producing springs

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Direct Pumping Systems

• Most found in agriculture and industrial settings

• May be tapped into by rural fire departments as needed (Continued)

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Direct Pumping Systems

• How they work– One or more pumps draw water from

primary source, transport to point of use

– If for drinking/domestic purposes, pumped into filtration and treatment facility

– From there, pumped into distribution system (Continued)

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Direct Pumping Systems

• Disadvantages– Total dependence on pumps– Dependence on electricity to run

pumps

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Gravity Systems

• Use primary water source located at higher elevation than distribution system, deliver water without pumps

(Continued)

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Gravity Systems

• Gravity provides pressure to transport water

• Gravity pressure adequate only when primary water source located more than 100 feet (30 m) higher than highest point in system

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Combination Systems

• Combination of direct pumping, gravity systems

• Used in majority of communities in North America

(Continued)

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Combination Systems

• How they work– Water pumped from treatment facility

to elevated storage tanks near point of use

– Water stored in tanks and delivered by gravity pressure

(Continued)

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Combination Systems

• If storage capacity adequate relative to consumption, extended power outage/pump failure will not affect reliability/availability

• Many industrial facilities have own combination water supply systems

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Water Treatment Facilities

• Treat water intended for domestic use to remove contaminants

• Filter out particulates and add chlorine to kill bacteria, other organisms

• May add fluoride to prevent tooth decay

(Continued)

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Water Treatment Facilities

• Main concern for fire protection– Mechanical breakdown, natural disaster,

etc., could disable facility’s pumps– Disabling pumping capacity would

seriously reduce volume, pressure of water available

• Another potential problem — Storage, use of large quantities of liquid chlorine

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Water Storage and Distribution Systems

• Water received from treatment facility, delivered to elevated storage tanks before being distributed

• Ability of water system depends on– Capacity, elevation of storage tanks– Condition, carrying capacity of mains

(Continued)

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Water Storage and Distribution Systems

• When water flows through pipes, movement causes friction that reduces water pressure

• Friction loss reduces volume, pressure of water available from fire hydrants connected to water distribution system

(Continued)

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Water Storage and Distribution Systems

• Types of hydrants– Dead-end hydrant– Circulating feed

• Grid system– Provides circulating feed from all

direction– Primary feeders– Secondary feeders (Continued)

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Water Storage and Distribution Systems

• Grid system– Distributors– Two or more primary feeders should

run from source to high-risk, industrial districts by separate routes

– Secondary feeders connect primary feeders and supply water from two directions to any point

(Continued)

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Water Storage and Distribution Systems

• Recommended sizes of mains– Residential areas– Business, industrial areas

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Water Main Valves

• Provide means for controlling flow of water through distribution piping

• Should be located at frequent intervals in grid system so only small sections are cut off if necessary to isolate parts of system for repairs

(Continued)

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Water Main Valves

• Spacing should be such that only minimum length of pipe is out of service at any time

• Should be operated at least once/year to keep working

• Water department should be able to open valves promptly when needed (Continued)

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Water Main Valves

• Indicating valves– Show position of gate or valve seat– Includes most valves in fire protection

systems– Post indicator valves (PIVs)– Outside stem and yoke (OS&Y) valves

(Continued)

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Water Main Valves

• Nonindicating valves– Normally buried/installed in utility

manholes– Can be operated aboveground

through valve box or may need special socket wrench on end of reach rod

(Continued)

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Water Main Valves

• Control valves– Can be indicating or nonindicating

types– Gate valves– Butterfly valves

(Continued)

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Water Main Valves

• Proper valve installation (spacing)– Necessary to close off one or two

hydrants from service while single break in main is being repaired

– Advantages reduced if all valves not properly maintained and kept open

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Water Mains

• Generally made of cast iron, ductile iron, asbestos cement, steel, PVC, plastic, or concrete

• Must be proper type for soil conditions, and pressures to which will be subjected

(Continued)

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Water Mains

• Water flow may be resisted by internal surface of pipe, encrustations, solidified sediments

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Pressure

• Force per unit area• Force that moves water through

conduit• Measured in pounds per square

inch (psi) or kilopascals (kPa)

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Static Pressure

• When little or no water flow, pressure that can be measured is static pressure

• Rarely found in public water supply system

• Defined in this context as normal pressure existing on system before water released from hydrant

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Flow Pressure

• Forward velocity pressure at discharge opening while water flowing

• Can be measured with pitot tube and gauge

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Residual Pressure

• Represents pressure left in system at specific location when water flowing

• That part of total available pressure not used to overcome friction/gravity while forcing water

• Provides indication of availability of additional water

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Summary

• Because water is the primary fire extinguishing agent used by firefighters in North America, fire departments must develop ways to transport the available water from its source to where it is needed.

(Continued)

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Summary

• Firefighters must know what water supply systems have been developed and what their responsibilities are when these systems are used.

(Continued)

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Summary

• Firefighters must know about water sources, pumping systems, gravity systems, and the system of underground water mains used to distribute the water.

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Review Questions

1.List sources of water supply for a jurisdiction.2.What are the three methods of moving water in a system?3.Describe the components of a grid system.

(Continued)

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Review Questions

4. What are static pressure, flow pressure, and residual pressure? 5.What are the two methods of holding a pitot tube properly?