Ch05 water supplies for fire protection systems

Chapter 5Water Supplies for Fire Protection Systems

Objectives• Define the terms pressure, flow, and

duration as they relate to the movement of water.

• Identify and describe the components of a water supply and distribution network.

• Discuss the difference between a municipal/public water system and a private water system.

Objectives• Describe how pumped, gravity, and

combined supply systems operate.• Define friction loss and discuss how it

affects water flow.• Define the terms static pressure and

residual pressure.

Objectives• List and discuss the characteristics of the

two types of NFPA-approved stationary fire pumps.

• Define the terms churn, rated performance, and peak performance in relation to stationary fire pump testing.

Introduction• Water demand of a community changes

throughout the day, week, month, and year.• Engineers need to determine if the source will

meet community needs, and if the delivery system is adequate.

• Fire flow models use various factors.• Determining the adequacy of the water supply is

one of the most critical factors in designing a water-based fire protection system.

Water Supply Systems• Source/supply network

– Pumped system• Supply comes from deep well or surface source such as

a lake• It is at a lower elevation than the location it serves and

requires a pump.

– Gravity system• Supply is stored at higher elevation than the location it

serves• Water flows at sufficient pressure on its own.

– Combined system uses both gravity and pumps

Water Supply Systems• Distribution network

– Transmission mains– Distribution mains– Service laterals/lines– For a distribution

network to be most effective, water should flow from multiple directions to any point in the system.

© A. Maurice Jones, Jr./Jones & Bartlett Learning

Water Supply Systems• Fire lines and fire mains

– Service laterals/lines that feed water-based fire protection systems

• “FL” (fire line)• “FM” (fire main)

– NFPA 24– The approving authority engineer

usually handles all inspections, tests, and certification of new public and private water lines.


Water Supply Systems• Water distribution system valves

– Valves that control water flow—public water systems

• Gate valves– Valves that control

water flow—private water systems

– Valves that control the direction of water flow © A. Maurice Jones, Jr./Jones & Bartlett Learning

Fire Hydrants• Overview

– Most important parts of any water distribution network

• Support manual firefighting operations

– Local building and fire codes• Required location• Number of hydrants in a

community• Distance from hydrant to hydrant


Fire Hydrants• Types of hydrants

– Dry barrel• Water is below frost line.

– Wet barrel • Water is in the barrel at

all times.– Wall, flush, and yard

© Jones & Bartlett Learning.

Fire Hydrants• Hydrant markings

– Hydrant barrels one color and the caps and bonnet a different color

– Expected water flow range

– Public, private, nonpotable hydrants

– Locator flag


Fire Hydrants• Hydrant inspection, testing, maintenance,

and service– Tests for new hydrants similar to those for

water lines– Need periodic testing/maintenance– Repainting, cleaning threads, lubricating the

stems, caps, plugs, and threads

Water Supply DesignConsiderations for Water-Based

Fire Protection Systems• Overview

– Obtain pressure and flow readings from the water source that will supply the system.

– System’s supply evaluated for:• Adequacy• Flow pressure• Duration

• Water flow test ensures water supply is adequate in:– Flow– Pressure– Duration

• Fire hydrant flow tests are commonly used.• The system may need to be reevaluated.• Depending on the deficiency, different options

are available.


Fire Protection Systems

• Water pressurization– Static pressure– Residual pressure– Flow rate– Gravity and – pressure tanks




• Stationary fire pumps– Fire pumps– Booster pumps– Special fire service pumps– Centrifugal pumps– Positive displacement

pumps– The flow and pressure reading

establishes the rated performance. • Basis for pump’s performance characteristics




• Fire pump assembly components– Drivers– Controllers– Transfer switch– Jockey or pressure – maintenance

pump– Control valves




• Fire pump assembly components (cont’d)– System relief valves– Bypass– Test headers and

flowmeters– Gauges– Eccentric or concentric

reducers/increasers




• Fire pump operation– Operates when there is sufficient loss of water

pressure in the system• Fire pump inspection, testing,

maintenance, and service– Acceptance testing– Periodic inspection, testing, maintenance, and

service



Summary• In most populated areas of the country, the water supply

system is typically controlled by a public utility, a local or state government, or a regional water authority. These organizations are responsible for the engineering, maintenance, and management of the municipal or public water system.

• The water supply system is divided into the supply/source network and the distribution network. The supply/source network takes the water into the system, treats and purifies it, and then sends it into the distribution network for storage and delivery purposes.

Summary• The water supply system supplies water for a

community’s domestic, commercial, industrial, and fire protection needs. In addition, it supplies water to privately owned water systems that support fire hydrants and water-based fire protection systems.

• Dedicated water lines, called fire lines or fire mains, connect the water supply to hydrants and fire protection systems. These lines should only supply the intended fire protection system, because their size must be adequate to meet the system demand.

Summary• Various types of valves control water flow and the

direction of water flow. These valves include nonindicating valves, indicating valves, check valves and backflow prevention devices.

• Fire hydrants offer fire fighters a ready water source for manual firefighting. Most jurisdictions require a hydrant where streets intersect, where the distance from hydrant to hydrant exceeds a maximum interval, and within 100 feet of a fire department connection.

Summary• The two most prominent types of hydrants are the dry

barrel, installed where temperatures fall below freezing, and the wet barrel, installed where temperatures remain above freezing.

• Water flow tests are used by the fire protection engineers and design professionals to determine if the water pressure, flow, and duration adequately meet the design requirements of various types of water-based fire protection systems. These tests might involve a 2-inch drain, a fire hydrant, or a fire pump.

Summary• To overcome pressure problems, design professionals

utilize gravity tanks, pressure tanks, or fire pumps to provide the needed pressure boost so the systems will operate at the required performance level.

Summary• There are two types of fire pumps listed or approved for

fire service duty: centrifugal and positive displacement. The centrifugal pump is the most common type of pump installed to support water-based fire protection systems. The positive displacement pump is the best choice for foam and water mist systems where a constant flow and pressure are necessary to protect the hazard.

Summary• A fire pump is part of an assembly of components, which

includes a controller and a driver. Other important components of the assembly include the transfer switch, pressure maintenance pump, relief valves, test header, and eccentric/concentric reducers/increasers.

Education

Ch05 water supplies for fire protection systems