Abastecimiento de Agua Ing

Chapter

7WATER SUPPLIES

Learning Objectives

Upon completion of this chapter, you should be able to:

List and explain basic considerations for preplanning and selecting water supplies.

Explain each of the five water supply systems typically used in fire pump operations.

Discuss the unique considerations for using each of the five water supply systems.

Describe the hydrant coding system as suggested by NFPA 291.

Explain how relay and tanker shuttle operations are designed.

164

Chapter 7 Water Supplies 165

NFPA 1002Standard for Fire Apparatus Driver/Operator

Professional Qualifications(2003 Edition)

This chapter addresses parts of the following knowledgeelements within sections 5.2.1, 5.2.2, and 5.2.4:

Problems related to small-diameter or dead-end mains

Low pressure and private water supply systems

Hydrant coding systems

Reliability of static sources

Position a fire department pumper to operate at a fire hydrantand at a static water source

INTRODUCTION

When an alarm is received, the first duty of a pump operator is to ensure the safearrival of the apparatus, equipment, and personnel at the scene. The next duty isto initiate fire pump operations. As stated earlier, fire pump operations consist ofthree interrelated activities:

1. Securing a water supply

2. Operating the pump

3. Maintaining discharge pressures

The critical first step of a pumping operation is to secure a water supply.Securing a water supply is the first step in the process of moving water from asource to the intake side of a pump. This particular activity is perhaps the mostchallenging and difficult of the three in that controlling the pressure and flow ofa supply is typically limited.

This chapter presents information as though the pump operator makes thedecision concerning which water supply to secure. In reality, this is not always the case. Depending on a departments standard operating procedures (SOPs), thedetermination of which water supply to secure can rest with any of the following:

Pump operator

Assigned officer

Pump operator and the officer (they share the responsibility)

Incident commander, water supply officer, or other officer within thecommand system

Regardless of who actually makes the decision, the pump operator should be capa-ble of evaluating and securing water supplies. Therefore, pump operators shouldbe familiar with the strengths and limitations of available water supplies.

Recall from Chapter 1 that water supplies come from three kinds of sources: theapparatus, static sources, and pressurized sources. Apparatus water supplies includewater tanks carried on the apparatus and are secured through onboard tank opera-tions. Static sources include ponds, lakes, and rivers and are secured through draft-ing operations. Pressurized sources include elevated towers and municipal watersupplies. Municipal water supplies are the most common pressurized source usedin the fire service and are secured through hydrant operations. Private water sup-plies, common in large industrial complexes, are similar in nature to municipal sys-tems. All three sources can be used in combination through relay operations andtanker shuttle operations to provide initial and sustained water supply to the scene.

Obviously, when only one source is available, pump operators have nochoices. However, when more than one source is available, pump operators shouldbe able to choose, or recommend, the water supply that maximizes the efficientand effective use of both the supply source and the apparatus to meet the flowrequirements of an incident.

This chapter discusses the pump operators task of securing a water supply,starting with basic water supply considerations. Then common supply systemstypically used in fire pump operations are presented to include onboard sup-plies, municipal private supplies, static supplies, relay operations, and tankershuttle operations.

BASIC WATER SUPPLY SYSTEM CONSIDERATIONS

The first few minutes of an emergency are typically accompanied by stress, anxi-ety, and confusion. In most cases, preplanning water supplies will help reduce thisstressful time of an incident. In addition, preplanning will help the pump opera-tor complete the task of securing a water supply in an efficient and effective man-ner. The following considerations should be included in the preplanning andselection of a water supply.

Required Flow. Determining the required flow, an estimated flow of waterneeded for a specific incident, is one of the first considerations when selecting awater supply. Considerations for calculating required flow are discussed in Sec-tion 4. In some cases, multiple pumpers are needed to provide the required flowfor an incident. In other cases, the required flow may not be known. In either case,a water supply should be selected that can provide enough water to flow thecapacity of the pump. In doing so, the pump operator is in the best position toassist with providing the required flow. The bottom line is that when securing awater supply, the amount of water the pump operator is expected to provideshould be known.

166 Section 3 Pump Procedures

required flowthe estimated flow ofwater needed for aspecific incident


Pump Capacity. Another important consideration when securing a watersupply is the capacity of the pump (Figure 71). In general, supplies should bechosen that are capable of providing enough water to allow the pump to flowcapacity. Larger capacity pumps may rule out some water supplies, while small-er capacity pumps will have a wider selection of supplies to choose from. Keep inmind that pumps, at draft, are expected to flow 100% capacity at 150 psi. Whenpump pressures in the operation reach 200 psi, the pump can only be expected todeliver 70% of its rated capacity. When pressures reach 250 psi, only 50% of itsrated capacity should be expected. In essence, increased pump pressures reducethe quantity of water the pump is able to flow. (See Rated Capacity and Perfor-mance in Chapter 4.)

Supply Hose Capacity. The size of supply hose is another considerationwhen selecting a supply source. Apparatus equipped with 212-inch supply hose may rule out some supplies, while those equipped with large diameter hose(LDH) may have a wider selection of supplies to choose from. In general, largerdiameter supply hose will provide less friction loss over longer distances.

Water Availability. Another important consideration is the availability ofthe source water. Several factors contribute to the availability of water. One is thequantity of water available. For example, a swimming pool may not provide asmuch water as a large lake. Other factors are the flow (gpm) and pressure (psi) atwhich water is available from the supply. Municipal supplies, for example, mayprovide water at a variety of flows and pressures. Finally, the physical location ofthe water is a factor. A marginal hydrant distant from the incident may not be thebest water supply if a good static source like a lake or pond is located closer to the incident. Water availability, then, relates to the quantity, flow, pressure, andaccessability of a water supply.

Supply Reliability. The reliability of a source should also be consideredwhen selecting a water supply. The supply reliability is the extent to which thesupply will consistently provide water. Another way of looking at it is the extentto which the supply fluctuates in flow, pressure, and quantity. For example, a river

Figure 71 The ratedcapacity andperformance of apump is usuallyidentified on ornear the pumppanel. Courtesy JoeReed.

water availabilitythe quantity, flow,pressure, and accessi-bility of a water supply

supply reliabilitythe extent to whichthe supply will consis-tently provide water

NoteA water supply should

be selected that can

provide enough water

to flow the capacity of

the pump.

or pond may not be a reliable supply if the water level changes frequently or isfrozen and tidal water supplies may change dramatically within a short period oftime.

Supply Layout. Finally, the supply layout hose should also be consideredwhen selecting a water supply. Supply layout is the required supply hose config-uration necessary to efficiently and effectively secure the water supply. The lay-out of supply hose may be affected by the type of source, the size of hose, the hoseappliances available, and the number and size of intakes on the pump. Therefore,a variety of supply hose configurations can often be used. Keep in mind, though,the more elaborate the supply configuration, the longer it will take to set it up. Forexample, connecting a supply hose to a pump located near the hydrant will nottake as long to secure as a relay or tanker shuttle operation. In general, the supplyconfiguration should be sufficient to provide the flow needed for an operation.

Although pump operators should be prepared to establish each kind of watersupply system, preplanning will make the task a little smoother and less stressful.This is especially true when considering the compressed time in which decisionsmust be made during an emergency. Pump operators should be familiar with thedifferent types of water supply systems, considerations for their use, and consid-erations for securing them.

ONBOARD WATER SUPPLIES

The onboard supply is simply the water carried in a tank on the apparatus (Fig-ure 72). The onboard water supply is used for several reasons. First, it is usedwhen no other water supply is available. In locations where this is a commonoccurrence, apparatus typically have larger onboard tanks. Second, it is usedwhen an incident requires only a small quantity of water, such as car fires andsmall brush fires. This saves time and energy when a supply source is not readi-


ENGINE

Figure 72 Mostpumping apparatuscarry at least aminimum onboardwater supply.

supply layout

the required supplyhose configurationnecessary to efficientlyand effectively securethe water supply

NotePreplanning will make

the task of securing a

water supply a little

smoother and less

stressful.

onboard supplythe water carried in atank on the apparatus


ly available. Third, it is used when an immediate water supply is deemed morecritical than the time it would take to secure a supply with greater flows. In thissituation, an alternate supply is secured while utilizing the onboard source. Final-ly, onboard water supplies can be used as a backup or emergency water suppliesin the event other water supply is interrupted.

Water Availability

An immediate and readily available supply of water is the main advantage of theonboard source. Although readily available, the onboard supply is the most lim-ited in terms of quantity of water. Most pumping apparatus have at least a smalltank of water on board. NFPA 1901 specifies minimum tank capacity for fireapparatus as follows:

initial attack apparatus: 200 gallons per minute

pumper fire apparatus: 300 gallons

mobile water apparatus/tanker: 1,000 gallons

Tank capacities of 500 to 1,000 gallons are common on many pumper fire appa-ratus and many mobile water apparatus have tank capacities over 2,000 gallons.NFPA 1901 also requires that the piping between the tank and the pump be capa-ble of flowing at least 250 gpm for tank capacities less than 500 gallons and mustbe able to flow 500 gpm for tank capacities of 500 gallons or larger. Greater flowsfrom the tank can be achieved by specifying a larger diameter pipe between thetank and the pump.

The length of time water can be supplied when utilizing the onboard waterdepends on the size of the tank and the flow of discharge lines. For example, a 134-inch preconnect flowing 125 gpm can be sustained for 8 minutes with a 1,000 gal-lon tank, 6 minutes with a 750 gallon tank, and 4 minutes with a 500 gallon tank.In comparison, a 212-inch line flowing 250 gpm can be maintained for 4, 3, and 2minutes with 1,000, 750, and 500 gallon tanks, respectively.

Supply Reliability

In general, the onboard water supply is a reliable source. A potential concern, how-ever, is not having water in the tank when on scene. This can occur when the tankis accidentally left empty or when the tanks level indicating device is malfunc-tioning showing the tank to be full when it is not. Another potential concern is thatair pockets may impede pumping the tank water. Air pockets may occur for sev-eral reasons: when the tank and piping develop leaks and holes, when air istrapped in the piping and pump, or when the pump is left dry to guard from freez-ing. Priming the pump to eliminate air pockets is usually all that is needed to beginpumping the tank water.

Supply Layout

The onboard water supply is by far the fastest supply to secure in that the supplyline is permanently attached. All that is required to secure the supply is to pull thetank-to-pump control valve. The tank-to-pump control valve opens and closes apassage from the tank to the pump. The tank is usually mounted higher than thepump to allow gravity to move water to the intake side of the pump. A controlvalve is also typically installed in the piping from the pump to the tank and hasseveral names: pump-to-tank, recirculating valve, and tank fill. This valveopens and closes a passage from the pump to the tank allowing the tank to berefilled from the pump. The two valves working together circulate water betweenthe tank and the pump. In addition, a tank level indicator is usually provided tomonitor water levels in the tank. The tank-to-pump and pump-to-tank controlvalves as well as the tank level indicator are commonly mounted on the pumppanel (Figure 73). Often, the onboard water supply can be pumped using eitherthe booster pump or the main pump.

In most cases, only small discharge lines are used in conjunction with theonboard tank. Typically, the discharge lines are preconnected and are either 1-inchbooster lines, 112-inch or 134-inch attack lines. When using the onboard tank, agood habit is to plan ahead for an alternate water supply should additional waterbe required. When an alternate supply is secured or when the incident is over, thepump operator should consider refilling the tank as soon as possible.


TANK LEVEL INDICATOR

TANK FILL

TANK TO PUMP

Figure 73 Onboardwater supplycontrol valves aretypically located onthe pump panel.Courtesy of KMEFire Apparatus.

NoteThe pump operator

should consider

refilling the tank as

soon as possible.


Often, the onboard supply is used to provide immediate water to the inci-dent. A difficult decision is how quickly water is needed at the scene. The quick-est delivery of onboard water is to simply drive the apparatus to the scene and startpumping. The major concern with this approach is the ability to secure anothersource before the onboard supply runs out. The second quickest way is to lay a linefrom the hydrant on the way to the scene. Although this approach takes a littlelonger to start flowing the onboard water, an alternate water supply can usuallybe secured within a reasonable time frame. This timing is critical when the totalquantity of water needed exceeds tank capacity.

MUNICIPAL SYSTEMS

Most densely populated areas in the United States utilize a municipal water sup-ply system. In many cases, a city, county, or special water district utilize a publicworks or water department to design, maintain, and test the municipal water sys-tem. Often, the difficult part is to not only maintain existing systems but to expandsystems in population growth areas as well as to upgrade systems as they wear outor become obsolete.

Municipal supplies deliver water to the intake side of the pump under pres-sure. They are used when water demands exceed onboard water supply ability orwhen the distance from the source to the incident is great. Hydrants are connect-ed via a water-main distribution system. Both hydrants and their water mains arecomponents of a municipal water supply system. Pump operators should be famil-iar with the municipal water system, its distribution system, and the types ofhydrants used in their service area.

Municipal Water Systems

Municipal water supplies commonly provide water for two purposes. First, theyprovide water for normal consumption such as household and industrial uses. Sec-ond, they provide water for emergency use to hydrants and fixed fire-protectionsystems. In some locations, two completely separate systems are used, one to pro-vide water for normal consumption and one to provide water for emergency use.More commonly, the same system provides water for both domestic consumptionand emergency use. When this is the case, fluctuating hydrant pressures andflows can be expected with the changes in domestic consumption.

The basic components of municipal water systems include a water supplycourse, a distribution system, and hydrants.

Municipal Water Supply Sources

The water supply source for a municipal system is obtained from either surfacewater such as lakes and ponds or groundwater such as wells or springs. In some

municipal supplya water supplydistribution systemprovided by a localgovernmentconsisting of mainsand hydrants

cases, a municipal system will use water from both sources. The water can bemoved from the source to the distribution system by means of a pumping system,gravity system, or a combination of the two. Pumping systems utilize pumps of suf-ficient size and number to meet the consumption demands of the service area.Typically, backup electrical power in the form of diesel generators and redundantpumps are maintained in case the primary electrical power or pumps fail. Gravi-ty systems use elevation as a means to move water from the supply to the distrib-ution system. A mountain lake providing water to a city in the valley is oneexample of a gravity system. Another example of a gravity system is an elevatedstorage tank (see Figure 74). Elevated storage tanks are common in many areasand can either be located on a hill or mountain or the tank itself may be elevated.Sometimes a combination pumping system and gravity system are used. In com-bination systems, the elevated storage tanks are used to assist pumping systemswith meeting peak demand needs or as an emergency or backup water supply. Inmany cases, the elevated storage tanks are filled at night when demands are lowerand pressures are higher. During the day, elevated storage tanks use gravity toassist pumps in meeting increased water demands.

In many cases, the water passes through a processing facility to filter and treatwater. This occurs most often when the system provides potable water for domes-tic consumption as well as for fire suppression. Typically, these facilities are


Figure 74 Elevatedstorage tanks aresometimes locatedon higher elevationsto further increasegravity.


designed to process water with sufficient capacity to handle peak domestic con-sumption and fire suppression needs; however, areas of rapid growth place aheavy burden on processing facilities to the extent that they are no longer able toprovide required flow to the community and/or for fire suppression efforts. Nat-ural disasters, equipment malfunctions, and terrorist activities may also impact theability of the processing facility to provide adequate water flows. Preplanning istherefore important to determine alternate water supplies. See Figure 75 for anillustration of the three systems.

TreatmentPlant and Storage

Lake

Pipe

Pipe

Treatment Plantand Storage

PipePumpPump House

Users

PipeRiver

Treatment Plantand Storage

Tank

Pump

Pipe

Pipe

LakeFigure 75Illustrations of (A) agravity-fed watersystem, (B) a pump-ing system, and (C)a combinationsystem.

A

B

C

Distribution System

Municipal water distribution systems consist of a series of decreasing sized pipes,call mains, and control valves that move water from the source or treatment facil-ity to individual hydrants and commercial and residential occupancies. The dis-tribution system typically starts with large-sized pipes, 16 inch or larger, calledfeeder mains, which carry water from the source or treatment facility to variouslocations within the distribution system. Larger-sized pipes are used to reduce theloss of pressure caused by friction an can carry water long distances. Because ofthis, feeder mains are typically spaced farther apart. Secondary feeder mains of intermediate size, 12 to 14 inches in diameter, carry water to a great number oflocations within the distribution system. Finally, distributors, the smallest sizepipe in the system at 6 to 8 inches in diameter, complete the system and connectdirectly to hydrants and residential/commercial customers (see Figure 76). Actu-al pipe sizes for a distribution system can differ considerably between one systemand other. The major factor for pipe size in all systems is the ability to provide the required flow. Simply put, larger demands require larger-sized pipes within thedistribution system.

Often, feeder mains and distributors are interconnected, allowing water to bedelivered to the same location through alternate routes. This interconnected sys-tem, sometimes called a loop or grid system has several important features. First,when the system supplies water from two or more directions, it helps reduce fric-


HYDRANTS

PRIMARY FEEDER SECONDARY FEEDERS

DISTRIBUTORS

DEAD-END

Figure 76 A griddistribution systemprovides betterwater suppliesbecause severalmains can feed onehydrant.


tion loss. Second, damage or maintenance on one part of the system can be isolatedusing control valves so that the distribution system remains in operation. Third,a high demand in one area will not adversely affect another area as much as if agrid system were not in place. Basically, water can flow from multiple locationsto compensate for a high consumption area. The ability to provide water from multiple locations can also be used to help maintain adequate water flow and pres-sure to high risk areas.

A hydrant supplied from only direction is called a dead-end main andhydrants located on the main are known as dead-end hydrants (see Figure 76).Should the dead-end main become damaged, all subsequent hydrants from thatpoint to the end of the main will become inoperable. Also, if a pumper beginspumping large quantities of water from one of the first hydrants on a dead-endmain, all subsequent hydrants will realize a significant reduction in water pressureand flow. The more water pumped from the hydrant, the less water is available forthe remaining hydrants on the dead-end main.

Control valves are used to direct water within a distribution system. Thesevalves can be opened and closed to redirect water within the system to isolate sec-tions of the grid or to enhance flow and pressure to sections of the grid. Therefore,control valves should be located in strategic locations within the grid to providemaximum flexibility. In some locations, only the public works or water depart-ment can operate control valves within the distribution system. Other locationsallow fire department personnel to operate control valves. Regardless, preplanningis essential, and pump operators should be familiar with all aspects of the distri-bution system, including control valve locations.

Indicating and nonindicating control valves are the two broad types of con-trol valves used in distribution systems. As the name implies, indicating valvesprovide a visual indication on the status of valveswhether open, closed, or inbetweenand are more commonly found in private distribution systems. Thetwo common types of indicating valves are the outside screw and yoke valve, com-monly referred to as an OS&Y valve, and the post-indicating valve, referred to asa PIV (see Figure 77). The OS&Y valve, typically used in sprinkler systems, ismade up of a treaded stem connected to a gate. The location of the stem within theyoke indicates the location of the gate. The PIV consists of a stem within a post thatis attached to the valve. When the valve is fully open or closed the words openor shut appear in the PIV. Nonindicating control valves are more commonlyfound in municipal distribution systems and are usually either buried or installedwithin manholes. Gated valves and butterfly valves are the two most commontypes used in distribution systems.

Hydrants

The two basic types of hydrants used by the fire service are wet and dry barrelhydrants, the latter being the most common. Wet barrel hydrants are typicallyused where freezing is not a concern. This type of hydrant is usually operated byindividual control valves for each outlet (Figure 78). As the name implies, water

NoteThe two basic types of

hydrant used by the

fire service are wet and

dry barrel hydrants.


Open

Closed

Handwheel Does Not Rise

OS&Y VALVE VISUAL INDICATION

VerticalIndicator Post

Finished Grade

Underground Fire Main

Wall PostIndicator Valve

OPEN

OPE

N

Stem rises as OS&Y valve is opened.Valve must be verified to be fullyopened at all times.

POST INDICATOR VALVESVISUAL INDICATION

Wall

Alarm Valve

Figure 77 The twobasic types ofindicating valvesinclude the OS&Yand the PIV.


is typically maintained in the hydrant at all times. Because each outlet is indi-vidually operated, supply hose can be connected and charged independently.

Dry barrel hydrants are typically used in areas where freezing is a concern.This type of hydrant is operated by turning the stem nut located on the bonnet ofthe hydrant, which opens the main valve at the base (Figure 79). The main valveis located at the bottom of the hydrant below the frost line. When the main valveopens, water enters the barrel for use through all the outlets. Because of this, sup-ply hose should be attached to outlets prior to opening the main valve. In addition,gated valves should be attached to unused outlets (Figure 710). In doing so, theoutlets will be available for use after the main valve is opened. When the main valve

STEM NUT

DISCHARGEOUTLET

GROUND LEVEL

BONNET

WATER MAIN

Figure 78 Typical schematic of a wetbarrel hydrant.

DRAIN HOLE

MAIN VALVE

WATER MAIN

DISCHARGE OUTLET

BONNET

STEM NUT

GROUND LEVEL

Figure 79 Typical schematic of a dry barrel hydrant.

wet barrel hydranta hydrant operated byindividual controlvalves that containwater within the barrelat all times; typicallyused where freezing isnot a concern

dry barrel hydranta hydrant operated bya single control valvein which the barreldoes not normallycontain water; typicallyused in areas wherefreezing is a concern

closes, the drain, also known as weep valve, opens allowing water to escape,returning the barrel to its normal state. One potential concern is that if the hydrantis not fully closed or opened when in use, the drain valve may remain slightly openallowing water to flow from the hydrant causing erosion and potential damage.

Both wet and dry barrel hydrants have a variety of outlet configurations andcan be found in a variety of positions. The normal configuration is one large out-let (4 inches or greater) and two 212-inch outlets (Figure 710). However, hydrantswith only two 212-inch outlets are also common (Figure 711). Most of these out-lets use American National Fire Hose connection screw threads (NH) couplings,although some locations still have special threads. In these cases, adapters arerequired to connect supply hose to the hydrant. Typically, hydrants are installedwith the 4-inch outlet facing the street and the 212-inch outlets parallel with thestreet. In addition, the outlets should be installed so they are not obstructed. How-ever, they are not always properly installed. Outlets can face almost any directionand can be obstructed in any number of ways. Some of the more common obstruc-tions occur when hydrants are improperly installed (Figure 712).


Figure 711 Some hydrants have only two 212-inchoutlets.

Figure 710 Additional lines can be attached to adry pipe hydrant while in use if gated valves areattached to unused outlets before the hydrant ischarged. Courtesy Greg Burrows.


Hydrants can be located almost anywhere and are often hidden from view(Figure 713). Therefore, fire departments utilize a variety of methods to assist inthe quick identification of hydrant locations. One common method is to use flu-orescent paint when painting the hydrant. Another common method is to placethree reflective bands on street poles, signs, or other tall objects located near a

Figure 712Improper installa-tion can reduce theeffective use of ahydrant.

Figure 713 Ahydrant is blockedfrom view by thefirst mail box on the right. Note thehydrant markerlocated in themiddle of the street (arrow).

hydrant. The reflective strips can also match the color code of the hydrants (seeTable 71). Another method gaining popularity is to place traffic reflective mark-ers (Figure 714) in the middle of the road adjacent to a hydrant (Figure 715). (Atraffic reflective marker can also be seen in Figure 713). To identify on which sideof the road the hydrant is located, the reflector can be offset on the side of thehydrant. Another method for identifying on which side of the road a hydrant islocated is to use two different colors on either side of the reflector, one color toindicate the left side and another color to indicate right side. Road reflectors dontwork well in areas where snow plows routinely work the streets in the winter. Inthese areas, a tall reflective flag or other indicating device is used. The device mustbe tall enough to be seen over snow drifts and snow banks.


Table 71 NFPA 291 suggests the following for classification and color coding hydrants.

Class Rated Capacity Color of Bonnets and Nozzle Caps

AA 1,500 gpm or greater Light blue

A 1,0001,499 gpm Green

B 500999 gpm Orange

C Less than 500 gpm Red

Figure 714 Hydrant traffic reflectors can helppump operators locate hydrants from a distance,especially at night.

Figure 715 Traffic reflectors are usually located nearthe middle of the road adjacent to the hydrant.


PRIVATE WATER SYSTEMS

Industrial, commercial, and large complexes or facilities often maintain their ownprivate water supply system. In most cases, these private water systems are simi-lar to municipal water systems. They can either receive their water from a munic-ipal water system or use surface or groundwater sources. In addition, privatewater supply systems can use a pumping system, gravity, or a combination of thetwo to move water from the source to the hydrant, standpipe system, or sprinklersystem. Typically, private water supply systems provide water for industrial/man-ufacturing use, employee use, and fire protection. Private fire protection systemsare typically maintained separate from other water systems. As with municipalsystems, private fire protection systems consist of a series of decreasing-sizedpipes, called mains, and control valves that move water from the source to indi-vidual hydrants and/or sprinkler and standpipe systems.

Water Availability

Municipal supplies, as a water source, have three main advantages. First, hydrantsprovide a readily available supply of water over an expanded geographical area.How available this water supply is depends on the extent to which hydrants aredistributed within an area. Second, hydrant flow capacities can be determined inadvance through flow tests. NFPA 291, Fire Flow Testing and Marking of Hydrants,identifies testing procedures and suggests that hydrants be classified and colorcoded based on their rated capacity (Table 71). Finally, municipal systems canprovide a sustainable supply for several hours. It is important to realize thatmunicipal water supplies are typically designed to provide required fire flows fora specific time frame, usually between 2 to 10 hours. When pumping less than therequired flow, hydrant operations can be sustained for longer periods. If pumps areused in the water system to move water, several types of pumps are installed.Some of the pumps run constantly, others turn on when additional pressure andvolume is required, and still others are maintained as emergency backup pumpscomplete with emergency electrical power sources.

Hydrant Flow Test

Hydrant flow testing provides the means to determine the available pressure andflow within municipal and private distribution systems. The information collect-ed during flow tests is critical for identifying and selecting hydrants that can pro-vide the estimated fire flows calculated during prefire planning activities. In somelocations, the public works or water department is responsible for conductinghydrant flow tests. In others, the pump operator conducts or assists with hydrantflow testing. Regardless, pump operators should be familiar with hydrant flow testprocedures.

Essentially, the flow test consists of measuring static and residual pressuresfrom one hydrant and measuring flow from one or more other hydrants. The datacollected during tests provide the means to calculate available hydrant flow at spe-cific residual pressure. NFPA 291, Recommended Practices for Fire Flow Testingand Marking of Hydrants, provides excellent information on all aspects of con-ducting flow tests to include the following.

Preparation (prior to conducting the flow test) Several considerations and actions to com-plete before conducting the flow test include the following:

Hydrant flow testing during periods of ordinary water demand will yieldmore accurate results based on realistic conditions.

Test hydrant location consideration may help to ensure minimum impacton traffic and to surface areas.

Use of hydrant diffusers can reduce the impact of erosion.

Select a test hydrant, sometimes referred to as the residual hydrant, andone or more flow hydrants.

Place a cap with pressure gauge onto the 212-inch test hydrant outlet.

To increase the accuracy of reading, ensure individuals at flow hydrantshave received training and have practice taking pitot gauge readings.

General Procedure The general procedures for conducting hydrant flow test are asfollows:

Step 1: the test begins with a static pressure reading at the test hydrant. Thereading is taken after fully opening the hydrant valve and removingthe air.

Step 2: open flow hydrant(s) one at a time until a 25 percent drop in resid-ual pressure is achieved.

Step 3: after a sufficient drop is noted, continue flowing to clear debris andforeign substances.

Step 4: take all readings at the same time; a residual reading at the testhydrant and flow readings using the pitot gauges at each of the flowhydrants.

Step 5: record the exact interior size, in inches, of each outlet flowed.

Step 6: after recording all readings, slowly shut down hydrants one at a timeto reduce the likelihood of a water hammer or surges within the system.

Equipment The following equipment is often required during hydrant flow testing.

pressure gauge mounted on an outlet cap, the pressure gauge calibratedwithin the past twelve months



pitot gauge for each hydrant; note: NFPA 291 requires gauges calibratedwithin the past twelve months

a hydrant diffuser can be used to reduce damage caused by large volumeflows from hydrants

hydrant wrenches

portable radios

Calculating Results First, calculate the discharge from hydrants used for flow duringthe test. The flow from hydrant pitot readings can be determined by either a chart,see Table 4.10.1(a) within NFPA 291, or by the following formula:

Q = 29.84 c d2p (71)where c = coefficient of discharge

0.90 for smooth and rounded outlets0.80 for square and sharp outlets0.70 for square outlets projecting into the barrel

d = diameter of the outlet in inchesp = pitot pressure in psi

When multiple hydrants are used in the flow test, calculate (or look up) each flowand then add them together.

Next, calculate the discharge at the specified residual pressure and/or desiredpressure drop using the formula:

QR = QF (hr0.54/hf0.54) (72)

where QR = predicted flow at specified residual pressureQF = total flow from hydrantshr = pressure drop to desired residual pressure (initial static

pressure readingdesired residual pressure)hf = pressure drop measured during test (initial static pressure

readingfinal residual pressure reading)

The formula can be computed using a calculator capable of logarithms or by look-ing up the values of pressure readings to the 0.54 power in a table. NFPA 291 sug-gests both a form to use to document flow test data and a form to graph results. Avariety of computer software programs are available to assist with hydrant flow cal-culations and reporting.

Reliability

Municipal systems generally provide a reliable supply of water; however, severalfactors may reduce the reliability of this supply source. First, the flow from hydrantsmay decrease over time based on gradual increases in municipal consumption or

through the normal deterioration of piping and components. The color coding ofhydrants, as suggested by NFPA 291, provides flow rates for a single hydrant.When multiple hydrants are used, individual hydrant flows may change dramati-cally. In addition, the color code indicates flows during normal municipal con-sumptions. During peak use hours, hydrant flow rates may again changedramatically. Finally, leaks, preventive maintenance, scheduled outages, and dam-aged or broken components may all lead to reduced flow capacity of hydrantsfrom time to time.

Supply Layout

Hydrant supply hose configurations can vary depending on the flow and pressureof the hydrant, the position of the apparatus, and the number and size of intakesavailable on the apparatus. The more complex the configuration, the longer it willtake to set up the supply operation. The first step, though, is to select a hydrant.In some cases, there is no choice in that only one hydrant is available. In general,hydrants closer to the incident should be selected to reduce the time to set up theoperation as well as to reduce the loss of pressure due to friction; however, in somecases a stronger hydrant (with more volume and pressure) that is farther away maybe picked over weaker hydrants closer to the incident. In addition, the number andsize of hydrant outlets may influence which hydrant to select. Finally, the pumpcapacity and the size of supply lines available will influence the selection of ahydrant.

Once the hydrant is selected, the next step is to determine supply line con-figurations. In general, larger supply lines should be used when possible. Supplylines should be laid to minimize bends and kinks to reduce losses in pressure fromfriction. Regardless of the configuration, the pump will be positioned either nextto the hydrant or some distance from the hydrant.

The pump can be positioned at the hydrant for several reasons. One reasonis that the hydrant is relatively close to the scene and attack lines can be advancedfrom that position. Another reason is when a reverse lay is conducted. A reverselay (see Figure 716) is when the apparatus stops at the scene, drops off attacklines, equipment, and personnel, and then advances to the hydrant. Another rea-son for the pump being located at the hydrant is when it is the first pump in a relayoperation. Finally, the pump may be located at a hydrant when increasing hydrantpressure to another pump by use of a four-way hydrant valve (see Figure 715).

Because hydrant outlets and pump intakes vary, a wide range of configura-tions is possible when the pump is located at a hydrant. The quickest way is to usea soft suction hose to connect directly into one of the main intakes. Another wayis to use a 50-foot section of LDH. When smaller-diameter-hose is used, two ormore lines can be connected from the hydrant. This is typically accomplishedusing wyes on the hydrant and siamese on the pump intake. Because hydrants arelocated at different distances from the curb and outlets can face just about any


reverse laysupply hose lineconfiguration whenthe apparatus stops atthe scene; dropsattack lines,equipment, andpersonnel; and thenadvances to thehydrant laying a supply line


direction, pump operators must realize that positioning the apparatus at hydrantswill vary. When possible, the configuration should provide enough water to pumpcapacity or deliver the required flow.

If the pump is not positioned at the hydrant, either a forward lay has beenconducted or the pump is being supplied as part of a relay operation. A forwardlay (see Figure 717), sometimes referred to as a straight lay, is when the appara-tus stops at the hydrant and lays a supply line to the fire. If the apparatus proceedsdirectly to the scene, a second apparatus can lay a line to or from a hydrant.When a supply line is laid to the pumper, the line is connected to one of thepumps intakes.

Hydrant

Fire Location

EngineDirection of Layand TravelFigure 716 A

reverse hose lay.

Hydrant

Direction of Layand Travel

Fire Location

EngineFigure 717 Aforward or straighthose lay.

forward laysupply hose lineconfiguration whenthe apparatus stops at the hydrant and asupply line is laid tothe fire

STATIC SOURCES

Static sources are those supplies such as ponds, lakes, rivers, and swimmingpools, that generally require drafting operations (Figure 718). Drafting is theprocess of moving or drawing water away from a source by a pump. Static sourcesare used for several reasons. First, they are used when hydrants are not available.Many communities simply cannot afford or dont need a municipal water system.Second, static sources are used when available hydrants cannot provide the need-ed flows. Finally, they are used when natural disasters or mechanical failurescause hydrant systems to shut down.

Drafting operations require the use of a special supply hose called hard suc-tion hose (Figure 719 see also Classification of Hose in Chapter 6). Hard suction hose is used because supply line pressures will be at or below atmosphericpressure within the hose. It is important to match the size of hard suction with therated capacity of the pump (Table 7-2). Hard suction hose too big or too small maymake it difficult or impossible to prime the pump. In addition, the ability to pumpcapacity may be significantly reduced. Pumpers that comply with NFPA 1901 willhave the appropriate size of hard suction hose for the rated capacity of the pump.

To keep debris from the static source from entering the pump, strainers areconnected to the end of hard suction hose. Note the strainer attached to the bot-tom section of hard suction hose in Figure 719. Care must be taken to keep thestrainer off the bottom of the water source to prevent clogging (Figure 720). Inaddition, if the strainer is too close to the surface, whirlpools may develop allow-


Figure 718 Example of a static water supply. Figure 719 Drafting operations require hard suctionhose. Pictured are the newer, more maneuverable,sections of hard suction. Courtesy Greg Burrows.

static sourcewater supply thatgenerally requiresdrafting operations,such as ponds, lakes,and rivers

draftingprocess of moving ordrawing water awayfrom a static source bya pump


ing air to enter the pump (Figure 721). The result may be either inefficientpumping or loss of prime.

Drafting operations typically require apparatus to position fairly close to thesource, as shown in Figure 721, because the height to which water can be draft-ed is limited. Recall that water is not sucked or pulled into the pump. Rather,when the priming system reduces the pressure in the pump (below 14.7 psi) at sealevel, water is forced into the pump by atmospheric pressure (14.7 psi). Water willrise approximately 2.3 feet for each 1 psi of pressure. If the priming device reduces

Figure 720 This strainer also keeps the hard suction off thebottom to prevent clogging. Courtesy Greg Burrows.

Figure 721 Thestrainer being usedin this draftingoperation floats onthe surface. It isdesigned to skimdebris free surfacewater while control-ling whirlpoolproduction.Courtesy ZiamaticCorporation.

Table 72 Rated capacity of hard suction hose.

Rated Capacity Hard Suction Size

750 gpm 412-inch

1,000 gpm 5 inch

1,250 gpm and above 6 inch

the pressure inside the pump from 14.7 psi to 9.7 psi (a 5 psi reduction), the atmos-pheric pressure, now 5 psi greater than the inside the pump, will force water to aheight of 11.5 feet (2.3 5 = 11.5 feet). If the priming system reduced the pressureto 0 psi, a perfect vacuum, how high will atmospheric pressure force the water?This height is called theoretical lift and can be calculated by multiplying 14.7 psi(atmospheric pressure) by 2.3 feet per psi, approximately 33.81 feet. Obviously,priming systems on apparatus come nowhere near creating a perfect theoreticallift. The general rule of thumb is to attempt to pump no more than 22.5 feet, or two-thirds of the theoretical lift.

Capacity tests for pumps are conducted at draft. In general, pumps are requiredto flow capacity through 20 feet of hard suction with a maximum height of 10 feet.Greater heights and longer supply lines reduce the ability to flow capacity.

Availability

Regional differences determine the availability of static sources. Some areas havemany sources, while others may have only a few. Where static sources are avail-able, access to the supply may be limited. For example, the banks of rivers may betoo steep or too soft to support the weight of the apparatus (Figure 722). The avail-able flow from different static sources also vary as well. The available water froma small pond will not be as great as a large river. Pump operators should be famil-iar with drafting locations and available flows for their service area


Figure 722 Thebanks of this staticwater supply willnot support theweight of a pumper.


Access and flow for static sources can be enhanced in several ways. One wayis to provide an adequate road to the drafting site (Figure 723). In doing so,access can be increased during seasonal and weather changes. Another way is toprovide a stable area close to the source where drafting operations can take placesafely. Dredging the immediate area surrounding the drafting location is anotherway to enhance the static source by helping to provide unrestricted flows. Final-ly, static source hydrants, sometimes called dry hydrants, can be installed (Fig-ure 724). These hydrants are simply prepiped lines that extend into the staticsource (Figure 725). Static hydrants can be used for natural static sources (ponds,lakes, and rivers) as well as artificial sources such as underground water tanks.These hydrants can be beneficial in that they reduce setup times, can increaseflows by using large lines, and can increase the number of access points to a stat-ic source. A disadvantage is sediment that may form in the piping requiring aback flush prior to priming the pump.

Reliability

Static water supply reliability is affected by three factors. The first factor is the sup-ply itself. Static supplies can change based on environmental and seasonal con-ditions. For example, droughts tend to diminish water supplies, while excessiverains may flood normal drafting locations or soften the ground thus restrictingaccess. In addition, excessive silt and debris may render the source unusable. In

Figure 723 Provid-ing an adequateroad will enhancethe availability of astatic source, espe-cially in areaswhere seasonalconditions impairaccess.

static source hydrantsprepiped lines thatextend into a staticsource.

the winter, the water may freeze, hindering access to the supply. Tidal water sup-plies can change dramatically within a short period of time. The second factor isthe pump and equipment used to draft the static source. Drafting is demanding forboth the pump and the pump operator. Pumps and equipment must be maintainedin good working order to efficiently and effectively use static sources as a supply.Finally, the pump operator is a factor. Pump operators must be thoroughly famil-iar with pump operations, priming operations, and drafting operations to reliablyuse static sources.


Figure 724Example of a staticsource hydrant.

WATER LEVELWATER LEVEL

STRAINER

Figure 725 Staticsource hydrants areprepiped lines thatextend into thestatic source.


Supply Layout

Setting up a drafting operation takes time, skill, and at least one person to assistthe pump operator. The first step is to position the apparatus as close to the sourceas possible. Next, hard suction hose and the strainer should be coupled, makingsure all connections are tight. Then the hard suction is connected to the pumpintake and the strainer placed into the water. The hard suction should not beplaced over an object that is higher than the pump intake. When this occurs, airpockets are likely to form that may hinder priming and pumping the static source.In addition, the strainer should be placed to ensure unrestricted flow. The last stepis to ensure that the pump is airtight. This means that every possible locationwhere air can enter the discharge or intake piping should be checked. Inlet andoutlet caps should be tightened and all control valves should be checked to makesure they are completely closed. In addition, the relief valve should be turned off,and bleeder valves should be tightened.

RELAY OPERATIONS

Relay operators are those operations in which two or more pumpers are connectedin-line to move water from a source to a discharge point. Relay operations are usedfor several reasons. First, they are used when a water source is distant from the inci-dent and cannot provide appropriate flows and pressures to the scene. Second, theyare used when a water source is relatively close to the incident but lacks pressure.Third, relay operations are used to overcome loss of pressure from elevation gains.

The original water supply can be either a static source or a hydrant in amunicipal source. Therefore, the considerations for static sources and hydrants arethe same for relay operations as they are for drafting operations. This section, then,discusses the unique considerations and setup requirements of relay operations.

Relay operations require at least two pumps: a supply pump and an attack pump. The supply pump, obviously is positioned at the supply, while the attack pump is the last pump in the relay. Additional pumps in the relay arecalled in-line pumps. Relay operations tend to take longer to set up and are usu-ally more complicated to operate (Figure 726).

PUM

PER

PUM

PER

PUM

PER5"

3"

3"3"3" 1 3/4"

ATTACK PUMPIN-LINE PUMPSUPPLY PUMP

Figure 726 Relayoperations requireat least two pumps,usually take longerto set up, and aremore complicatedto operate.

relay operationwater supplyoperations where twoor more pumpers areconnected in line tomove water from asource to a dischargepoint

NoteThe hard suction should

not be placed over an

object that is higher

than the pump intake

because air pockets are

likely to form that may

hinder priming and

pumping the static

source.

NoteRelay operations

require at least two

pumps: a supply pump

and an attack pump.

A relay operation is similar to the operation of a two-stage pump operatingin the series mode. Recall from Chapter 4 that in the series mode, water is dis-charged from one impeller to the intake of the second impeller. In a relay opera-tion, water is discharged from one pump to the intake of a second pump. However,water flows through supply hose between the two pumps rather than through fixedpiping within the pump. In the series mode, the flow available to the secondimpeller is limited by the flow produced by the first impeller. The same holds truefor relays in that the flow available to the second pump is limited by the flow gen-erated by the first pump. For this reason, the largest pump should be placed at thesource when possible. In a series mode, pressure is doubled as the second impellertakes the pressure generated by the first impeller and adds the pressure it gener-ates. The same concept holds true for relay operations in that the second pump cantake advantage of the pressure provided by the first pump. However, in a relay thepressure generated by the first pump will be reduced by friction in hose lines andelevation when it enters the intake of the second pump.

The major difference between a relay operation and a pump operating in theseries mode is the ability to independently control changes in pressure and flow.In a series mode, each impeller rotates at the same speed. Therefore, a change inflow in the first impeller will automatically be pumped by the second. Further, achange in pressure by the first impeller will automatically be doubled as it pass-es through the second impeller. In each case, the change is predictable and auto-matic. In a relay operation, the impellers in one pump do not rotate at the samespeed as other pumps and are therefore able to generate different flows and pres-sures. When the pumps are connected and flowing, changes in pressures andflows in one pump affect the entire system.

One of the major difficulties in relay operations is how to control changes inpressures and flows. When additional water is needed for the incident, flow mustincrease from the supply pump and all other pumps in the relay. If an attack lineis shut down, pressure can increase throughout the system. The manner of con-trolling pressures and flows in a relay depends, in part, on the type of relay used.In general, relay operations can be either open or closed.

Closed Relay Operations

In a closed relay system, water enters the relay at the supply and progressesthrough the system to the attack pump. This system is similar to the pump oper-ating in the series mode in that all the water and pressure is delivered from onepump to the next pump in the relay. Because all the water is contained, control-ling pressure and flow requires that each pump be changed. For example, if anattack line is shut down, the attack pump would compensate for reduced flows aswould each of the pumps in the relay. Controlling pressure and flow with this sys-tem is difficult, at best, in that changes occur quickly and affect the entire relayoperation. Pump operators would find it difficult to keep up with needed changesat each pump as well as to coordinate efforts with other pumps in the relay.


closed relayrelay operation inwhich water is con-tained within the hoseand pump from thetime it enters the relayuntil it leaves the relayat the discharge point;excessive pressure andflow is controlled ateach pump within thesystem

NoteOne of the major

difficulties in relay

operations is how to

control changes in

pressures and flows.


Open Relay Operations

In an open relay system, flow and pressure are not contained within the total sys-tem. In other words, all the flow and pressure from one pump is not always deliv-ered to the next pump. This design allows a continuous flow through the relay,which reduces the need to make constant changes as well as reducing the overalleffect of pressure changes within the system. Open systems can be set up accord-ing to one of three methods.

One method simply dedicates and maintains an open discharge line from the attack pump to flow excess water. In this case, once flow is initiated, only theattack pumper is required to make changes. If one or more attack lines are shutdown, the pump operator simply increases flow through the dedicated line. Thisalso has the benefit of quicker responses to change as well as having additionalwater readily available. Care must be taken concerning where the excess water isflowing. This system tends to pump more water than is actually needed.

Another method is to have the relay deliver its water directly into a portabletank rather than directly into the intake of the attack pump. The attack pumpwould simply draft from the portable tank. In this case, the relay operates contin-uously without needing constant changes. If attack lines are shut down, the attackpump reduces flow and the portable tank simply overfills. This system also pro-vides ready access to additional water if needed.

Finally, the relay can be set up to take advantage of new automatic intake anddischarge relief valve requirements. In this case, each pump sets its relief valves(s)to control pressure increases within the relay. When pressures rise above the set-ting, relief valves automatically open to dump excess pressure. This system has theadded benefit of being able to automatically increase flows by simply increasingthe relief valve setting. Relief valve requirements are discussed in both NFPA 1901and NFPA 1962.

Designing Relays

Step One The first step in relay design is to evaluate each of the following factors:

Amount of water to flow

Available water at the supply

The size and number of pumps available

The size and length of supply hose available

The distance from the source to the incident

The weakest of these factors will be the limiting factor of the relay design. Forexample, a relay operation capable of flowing 1,000 gpm is limited when the sup-ply can only provide 500 gpm. In addition, a 1,000-gpm pump equipped with 500feet of 212-inch supply hose is not able to pump the quantity or distance as thesame pump equipped with 500 feet of 4-inch supply hose.

open relayrelay operation inwhich water is notcontained within theentire relay system;excessive pressure iscontrolled by intakerelief valves, pressureregulators, anddedicated dischargelines that allow waterto exit the relay atvarious points in thesystem

Two of the more important factors to consider in the design of a relay are theamount of water the relay is expected to flow and the water available at the sup-ply. The basic design of the entire system will be affected by these factors. Anoth-er important consideration is the number of pumps available and their ratedcapacity. Obviously, pumps must be of sufficient capacity to provide the requiredflow in the relay. Pumps must also be able to generate sufficient pressures tomove this flow over a distance. When designing a relay, it is important to keep inmind the relationship between flow and pressure. When pressure increases, flowsdecrease. Recall, as mentioned earlier in this chapter that pumps at draft areexpected to flow 100% capacity at 150 psi, 70% capacity at 200 psi, and 50%capacity at 250 psi. In essence, increased pressures reduce the quantity of waterthat can be pumped, which is often the case during relay operations.

The size of hose available for use in the relay is another important consider-ation from two perspectives. First, it is important to keep in mind the relationshipof hose size with the amount of water it can flow and the friction loss it develops(see classification of hoses in Chapter 6). In general, larger diameter hose will flowmore water and have less friction loss than smaller diameter hose. Second, thehighest operating working pressure of the hose must be considered. For mediumand small diameter hose attack lines, the highest operating pressure is 275 psi,while the highest operating pressure for LDH supply lines is 185 psi according toNFPA 1961 and 1962. Because of the nature of relay operations, supplying waterover distances, pressures can easily exceed the 185 psi operating pressure of LDHsupply hose. To safely utilize LDH, NFPA 1962 requires a discharge relief devicewith a maximum setting no higher than the service test pressure of the hose in use.

There are two additional considerations related to pressure in relay opera-tions. The first relates to the gain or loss in pressure resulting from changes in ele-vation within the system. In general terms, pumping uphill is harder thanpumping downhill; more pressure is needed to pump water uphill and less pres-sure is needed to pump water downhill. For every one foot of elevation gain, pressure will increase .434 psi. If the average height of a single story is 10 feet, thenthe pressure gain will be 4.34 psi (.434 psi/ft 10 ft = 4.34 psi). As a rule of thumb,add or subtract 5 psi for each story (or each 10 feet) in elevation gain or loss. (Addi-tional information on pressure gain and loss is presented in Section 4 of thisbook.) Another consideration in the design of a relay is the pressure required at theintake of each pump within the relay. When one pump flows water to the next,friction loss in the hose will reduce the discharge pressure. The goal is to provideenough pressure from the first pump to cover the loss in pressure from friction sothat at least 20 psi remains when water enters the second pump. The purpose ofmaintaining a minimum of 20 psi is to ensure that the pump will not cavitate.Recall that cavitation can damage pumps, cause a loss of prime, and reduce pump-ing efficiency. Cavitation is discussed in greater detail in Chapter 9.

Finally, the distance between the source and the incident is important. Ingeneral, the farther the distance, the more resource-intensive the relay will be.When large flows are required, either large pumps with LDH will be spaced quite


NoteTwo of the more

important factors in

the design of a relay

are the amount of

water the relay is

expected to flow and

the water available at

the supply.

NoteWhen designing a relay,

it is important to keep

in mind the

relationship between

flow and pressure.


some distance apart or smaller pumps with medium diameter hose will be spacedrather close together in the relay (Figure 727). In reality, a variety of combinationscan occur, each depending on the weakest component in the system.

Step Two When all of these factors are considered, the next step is to determine thedistance between pumpers. Unless each pump has the same capacity and availablehose, the distance between one pump and the next will be different. The goal isto maximize the distance between pumps while providing the required flow. Thisis accomplished by first determining the pump discharge pressure that can providethe required flow in the relay. For example, a relay operation requiring 500 gpm

500' OF 3"

750

GPM

PUM

PER

750

GPM

PUM

PER

750

GPM

PUM

PER

750

GPM

PUM

PER

ATTA

CKPU

MPE

R

750

GPM

PUM

PER

1500

GPM

PUM

PER

1500

GPM

PUM

PER

1500

GPM

PUM

PER

ATTA

CKPU

MPE

RAT

TACK

PUM

PER

ATTA

CKPU

MPE

R

100%@150 PSI

100%@150 PSI

50%@250 PSI

50%@250 PSI

250' OF 3" 250' OF 3" 250' OF 3" 250' OF 3"

SUPPLYPUMPER

EACH RELAY IS FLOWING 750 GPM

IN-LINE PUMPERS

1,150' OF 4"

500' OF 3"

2,000' OF 4"

Figure 727 When distances between the incident and the source increase, relay operation resources increase as well.

can be provided by a 750-gpm pump operating at 200 psi (70% capacity) or a1,000-gpm pump at 250 psi (50% capacity).

The next step is to determine the distance between pumps. When the waterleaves the discharge side of the pump, the pressure will be reduced by friction aswater travels to the next pump. The question, then, is how far can the water trav-el until the pressure is reduced to 20 psi (the minimum intake pressure for pumpsin a relay)? The following formula can be used to determine this distance:

(PDP 20) 100 / FL (73)

where PDP = pump discharge pressure20 = reserved intake pressure (psi) at the next pump

100 = length (feet) of one section of hose (the most commonlength of hose is 50 feet; however, friction losscalculations use 100-foot increments/sections)

FL = Friction loss (psi) per 100-foot section of hose

Take, for example, a 750-gpm pump flowing 500 gpm through 4-inch hose at200 psi pump discharge pressure. The friction loss in 4-inch hose flowing 500 gpmis 5 psi per 100 feet (see chart on friction loss in Appendix F). In this example, thepressure in the hose will be 20 psi after water travels a distance of 3,300 feet [(185 20) 100 / 5 = 3,300]. Note that the pump discharge pressure was reduced to 185 to comply with supply hose maximum operating pressure. What distance willwater travel if the 500-gpm relay flow is provided by a 1,000-gpm pump with 3-inch supply line? First, the 1,000-gpm pump can provide 500 gpm at a pump dis-charge pressure of 250 psi. Next, the friction loss in 3-inch hose flowing 500 gpmis 20 psi per 100 feet. In this example, water will travel 1,150 feet before it reach-es 20 psi [(250 20) 100 / 20 = 1,150]. In comparison, if the 3-inch hose isreplaced with 212-inch hose in the last example, water will travel 460 feet whenthe pressure is reduced to 20 psi [(250 20) 100 / 50 = 460].

Step Three The last step is to lay the supply lines and position the pumps. The largestpump should be positioned at the water source whenever possible. The next pumpin the relay simply lays a line equal to the predetermined distance. When all thelines are in place, the relay operation can begin. The steps for initiating relay flowsare discussed in Chapter 8.

TANKER SHUTTLE OPERATIONS

Tanker shuttles are those operations where apparatus equipped with large tankstransport water from a source to the scene (Figure 728). Tanker shuttle operationsare used for two general reasons. First, they are used when pressures and flow fromthe supply source or pump, hose size, and distance limit the ability to move waterfrom the supply to the incident. Second, they are used when obstacles such as ele-


tanker shuttlewater supply opera-tions in which theapparatus is equippedwith large tanks totransport water from asource to the scene


vation, winding roads, intersections, and railroad crossings limit the use of othersupply methods.

The components of a tanker shuttle include multiple tankers, pumps, a fillsite where tankers receive their water, and a dump site where tankers unload theirwater (see Figure 729). As with relay operations, the fill site supply can be eithera static source or a hydrant. This section, then, discusses the unique considerationsand setup requirements for tanker shuttle operations.

Shuttle Equipment

The equipment used in shuttle operations includes pumpers, tankers, portabledump tanks, and jet siphons. At least one pumper is required at the scene and usesthe water delivered by the shuttle to supply attack and exposure lines. Typically, thepumper will either draft from a portable tank or will be supplied under pressureby a nurse tanker. Other pumps can be located at the fill site to assist with rapidfilling of tankers or at the dump site to assist in the movement of water to thescene. For example, limited access to the scene may require that tankers delivertheir water some distance from the scene. In this case, an additional pumper isrequired to move water from the dump site to the attack pumper.

Tankers used in shuttle operations should be sufficient in capacity to providerequired flows. According to NFPA 1901, tankers should have a minimum capac-ity of 1,000 gallons. In addition, the tank must be able to both fill and unload at arate of 1,000 gpm. Adequate ventilation is also required to ensure that the tank isnot damaged during filling and unloading operations. The weight of the tanker is an important consideration for maintaining control as well as weight limits ofroads and bridges. Consider the weight of water in a 1,000-gallon tanker. Since theweight of one gallon of water is 8.35 pounds, the weight of 1,000 gallons is 8,350pounds (8.35 lbs per gal 1,000 gal = 8,350 lbs), or 4.175 tons (8,350 lbs 2,000lbs per ton = 4.175 tons). In general, smaller tankers are better for short-distance

Figure 728Apparatus equip-ped with large tanksare used in tankershuttle operations.Courtesy KME FireApparatus.

shuttles because they are able to load and unload water at a faster rate than larg-er tankers, which are better suited for longer distances.

Portable dump tanks and jet siphons are valuable pieces of equipment forshuttle operations. Portable tanks provide the means to unload tanker water for useby a pump (Figure 730). These tanks can be set up in almost any location wherethe ground is relatively level. Most portable dump tanks have a capacity of 1,000


Fill S

ite

PUMPER PUMPER

Dump Site

TANKER

TANK

ER

TANK

ER

Figure 729 Major components within a tanker shuttle operation.

portable dump tanka temporary reservoirused in tanker shuttleoperations thatprovides the means tounload water from a tanker for use by apump

jet siphondevice that helpsmove water quicklywithout generating alot of pressure andthat is used to movewater from oneportable tank toanother or to assistwith the quick off-loading of tankerwater


to 3,000 gallons. Some are equipped with special devices to ease filling and trans-ferring from one tank to another. Jet siphons (Figure 731) are devices that helpmove water quickly without generating a lot of pressure (Figure 732). They areused to move water from one portable tank to another (Figure 733) or to assist inthe quick off-loading of tanker water.

Figure 730 Portabletanks are an essen-tial piece of equip-ment in mostshuttle operations.Courtesy ZiamaticCorporation.

Figure 731 Exampleof two different jetsiphons.Courtesy ZiamaticCorporation.


Figure 732 Jetsiphons use verylittle water andpressure to movelarge quantities ofwater. CourtesyGreg Burrows.

Figure 733 Jetsiphons move waterfrom one drop tankto another. CourtesyZiamaticCorporation.


Designing a Tanker Shuttle

Although the specific design of a tanker shuttle will vary from one operation toanother, three basic components exist in all shuttle operations: the fill site, thedump site, and the shuttle flow capacity. Each of these components must be care-fully coordinated in order to efficiently and effectively supply water.

Fill Site Refilling tankers occurs at the fill site. Obviously, the goal is to fill thetankers in a fast and efficient manner. One consideration for a fast and efficient filloperation is the source used to supply the tankers. Both hydrants and staticsources can be used to fill tankers. The most efficient method of filling a tank isto connect a hydrant directly to the tanks intakes (Figure 734). When hydrantpressures are weak, a pumper may be used to decrease fill times. When hy-drant flows are low, a portable dump tank can be used to allow a pumper to draftwith greater flows. If a tank does not have an intake valve, the less efficient methodof filling the tank from the top must be used.

A second consideration for a quick and efficient fill operation is to provideadequate access to the fill site. In addition, the fill station should be set up to quick-ly connect and disconnect fill lines. If possible, the fill site should have two com-plete sets of fill lines available. While one tank is being filled, the second tankercan be connected and standing by. Filling two tankers at the same time may actu-ally increase fill times.

Figure 734 The fillsite is the locationwhere tankersreceive water.Courtesy GregBurrows.

fill sitelocation where tankersoperating in a shuttlereceive their water

NoteThe goal at the fill site

is to fill the tankers in

a fast and efficient

manner.

Finally, safety should be considered at fill sites. One potential safety concernis that apparatus will be moving in close proximity to personnel and equipment.Another concern is adequate venting when a tank is being filled. Improper vent-ing can be a significant hazard to both equipment and personnel.

Dump Site The dump site is the location where tankers deliver their water. The goal,again, is to quickly unload the water and head back to the fill site. As with the fillsite, issues of access and safety must be considered. Several options are availablewhen delivering the tankers water. Tankers can deliver their water directly to theattack pump, to another tanker (called a nurse tanker), or to a portable dump tank(Figure 735). Each tanker should carry a portable dump tank so it can quicklyunload its water and head to the fill site. In some cases, the dump site will havemultiple portable dump tanks allowing several tankers to unload their water at thesame time. The dump site should be located where adequate room is available fortankers to maneuver.

Shuttle Flow Capacity Shuttle flow capacity is the volume of water that can be pumpedwithout running out of water. The flow capacity of a shuttle is limited by the vol-ume of water being delivered and the time it takes to complete a shuttle cycle. Thevolume of water being delivered depends on the size and number of tankers. The shuttle cycle time is the total time it takes to dump water and return withanother load. The cycle time includes the time it takes to fill the tanker, the timeit takes to dump its water, and the travel distance between the fill and dump sta-


Figure 735 Tankerdumping waterdirectly into aportable dumptank. CourtesyZiamaticCorporation.

dump sitelocation where tankersoperating in a shuttleunload their water

shuttle flow capacitythe volume of water atanker shuttle opera-tion can provide with-out running out ofwater

shuttle cycle timethe total time it takesfor a tanker in ashuttle operation todump water andreturn with anotherload; including thetime it takes to fill thetanker, to dump thewater, and the traveldistance between thefill and dump stations


tions. In addition, the time a tanker must wait, if any, while other tanks are fillingor dumping is included in the cycle time.

Individual shuttle tanker flow capabilities can be determined by dividingtank volume by the time it takes to complete a cycle. For example, a 1,500-gallontanker that can complete a cycle in 10 minutes will have a shuttle flow rating of 150gpm (1,500 / 10 = 150 gpm). Cycle times may vary because different size tanks canfill and dump their water at different speeds. In addition, several fill sites may be used that will have different travel times. A 1,000-gallon tanker with an 8-minute cycle time will have a shuttle flow capacity of 125 gpm. When the twotankers are utilized in the same shuttle, the combined shuttle flow will be 275 gpm.

Combined shuttle flows can be calculated by adding individual tank flows(as in the previous example) or by adding the volumes of all tankers and dividingthe average cycle time for all tankers. In this case the total volume would be 2,500and the average cycle would be 9 minutes, for a total combined flow of 277 gpm(2,500 / 9 = 278 gpm). The slight difference between the two methods is the resultof averaging the cycle times.

!SafetyImproper vent-ing while filling a tank

can be a significant

hazard to both equip-

ment and personnel.


S U M M A R Y

The first step in fire pump operations is securinga water supply. The basic water supplies availableto pump operators are onboard tanks, staticsources, and municipal systems. These sourcescan be used in combination with relay operationsand tanker shuttle operations. In reality, any andall of the water supplies can be used in a variety ofconfigurations. The onboard water source is by farthe fastest, yet most limiting. Municipal water sup-plies are by far the most common. A variety ofhose layouts are available depending on requiredflow, pump size, hose size, and appliances avail-able. Drafting operations from static sources tend

to take longer to set up and are demanding on boththe apparatus and the pump operator. Relay oper-ations and tanker shuttle operations should bedesigned rather than just pieced together.

The most important concept in securing awater supply is knowing the expected flow. Sim-ply selecting the first available source may lead toinefficient utilization of the source and pump. It isalso important to understand the considerationsfor each of the water sources. Preplanning willmake the hectic first minutes of an incident a lit-tle less stressful for the pump operator.

R E V I E W Q U E S T I O N S

Key Terms and Concepts

On a separate sheet of paper, identify and/ordefine each of the following:

1. Required flow

2. Supply layout

3. Onboard supply

4. Municipal supply

5. Wet barrel hydrant

6. Dry barrel hydrant

7. Reverse lay

8. Forward lay

9. Static source

10. Drafting

11. Static source hydrants

12. Relay operation

13. Tanker shuttle

14. Fill site

15. Shuttle cycle time

Multiple Choice and True/False

1. The estimated flow of water needed for a spe-cific incident is called

a. available flow. c. critical flow.

b. required flow. d. incident flow.

2. In general, larger diameter supply hose willprovide more friction loss over longer dis-tances than smaller supply hose.

____ True

____ False

3. Each of the following factors contribute tothe availability of water except

a. quantity. c. accessibility.

b. flow. d. pump capacity.

4. Supply reliability is the extent to which thesupply will consistently provide water.

____ True

____ False


5. Which of the following water supplies is usu-ally the easiest to secure yet often the mostlimited?

a. municipal systems c. rivers

b. ponds d. onboard tank

6. How long can a 1,000-gallon onboard watertank sustain two 150-foot 134-inch hose lineseach flowing 125 gpm?

a. 2 minutes c. 6 minutes

b. 4 minutes d. 8 minutes

7. Typically, the same municipal water supplysystem will provide water for both normalconsumption such as household and indus-trial uses, as well as for emergency use tohydrants and fixed fire-protection systems.

____ True

____ False

8. The type of hydrant usually operated by indi-vidual control valves for each outlet is calleda(an)

a. individual outlet hydrant (IOH).

b. dry barrel hydrant.

c. wet barrel hydrant.

d. None of the above are correct.

9. Which of the following NFPA standards sug-gests that hydrants be classified and colorcoded based on their rated capacity?

a. 291 c. 1002

b. 1500 d. 1901

10. A hydrant with a red bonnet would mostlikely flow ________ gpm according toNFPAs hydrant classification system.

a. less than 500

b. between 500 to 750

c. between 500 and 1,000

d. greater than 1,000

11. If the pump is located at the hydrant, whichof the following has not occurred?

a. reverse lay

b. forward lay

c. first pump in a relay

d. boosting pressure using a four-wayhydrant valve

12. Drafting is the process of moving or drawingwater away from a source through hard suc-tion hose to the suction side of a pump usinga suction process.

____ True

____ False

13. If the priming system reduced the pressure to0 psi, a perfect vacuum, water would beforced to a height of ________ feet, alsoknown as theoretical lift.

a. 7.35 c. 22.5

b. 14.7 d. 33.81

14. Because priming systems come nowhere nearcreating a perfect theoretical lift, the generalrule of thumb is to attempt to pump no morethan two-thirds of the theoretical lift, whichis

a. 7.35 feet. c. 22.5 feet.

b. 14.7 feet. d. 33.81 feet.

15. Which of the following best describes a sta-tic hydrant?

a. prepiped lines that extend into a watersource

b. wet or dry barrel hydrant when no wateris flowing

c. hydrant that is identified as being out ofservice

d. no such hydrant


16. All of the following are factors that affect sta-tic water supply reliability except

a. environmental and seasonal conditions.

b. condition of hydrants and water mains.

c. pump and equipment used to draft.

d. pump operators drafting knowledge andskill.

17. One of the major difficulties in relay opera-tions is

a. walking from one pumper to the next.

b. having enough pumpers to use in therelay.

c. ensuring that an adequate water supplyis chosen.

d. how to control changes in pressures andflows within the system.

18. A relay where water enters at the supply andprogresses through the system to the attackpump is called a(an)

a. relay system.

b. open relay system.

c. traditional relay.

d. closed relay system.

19. According to NFPA 1961, supply hose oper-ating pressure should not exceed

a. 150 psi. c. 200 psi.

b. 185 psi. d. 250 psi.

20. The second pumper, all in-line pumpers, andthe attack pumper should maintain at least________ psi intake pressure.

a. 5 c. 35

b. 20 d. 50

21. The weight of water in a 1,500-gallon tankerweighs a little over

a. 2 tons. c. 6 tons.

b. 4 tons. d. 8 tons.

22. A hydrant with an orange bonnet can deliv-er which of the following flows ranges?

a. 200 to 500 gpm c. 1,000 to 1,500 gpm

b. 500 to 999 gpm d. 1,500 gpm or greater

Short Answer

On a separate sheet of paper, answer/explain eachof the following questions:

1. Explain the importance of preplanning watersupplies.

2. When the required flow is unknown, whatshould govern the selection of a watersource?

3. What effect do higher pump pressures haveon the ability of a pump to flow capacity?

4. What effect does the size of hose have on theability to move water?

5. What factors contribute to water availability?

6. What affects supply reliability for the watersources?

7. What affects the supply hose layout?

8. Why is it important to fully open or close drybarrel hydrants?

9. List four factors that may reduce the reliabil-ity of municipal water supply systems.

10. If the pressure inside a centrifugal pump isreduced to 8.7 psi, how high will atmo-spheric pressure raise water?

11. Explain the limitations of using LDH as asupply between pumps in a relay.

12. List two reasons for using a tanker shuttleoperation.


A C T I V I T I E S

1. Identify all usable static sources within yourresponse district.

2. Determine two potential relay operationswithin your response district. If hydrants arethe predominate water supply, assume sev-eral hydrants are out of service.

3. Develop specific procedures and forms toconduct flow testing using NFPA 291 as aguide.

P R A C T I C E P R O B L E M S

1. Determine how long a 500-gallon tank and a1,000-gallon tank can sustain two 112-inchlines flowing 100 gpm each.

2. Design a relay using the following informa-tion and provide the information requested:

Required relay flow of 750 gpm

Distance between pump and incident is1,500 feet

Water supply is a hydrant with an orangebonnet

Pumpers and hose available:

P1 = 750-gpm pump with 500 feet of 212-inch

P2 = 750-gpm with 1,000 feet of 4-inch

P3 = 1,500-gpm with 600 feet of 3-inch

a. Where will you place each of thepumpers?

b. What will be the distance between eachpump?

3. Determine the individual and combinedshuttle flows using the following informa-tion, where fill time and dump time includesconnecting and disconnecting hose:

T1: Tank size 1,000 gallonsFill time 3 minutesDump time 2 minutesTravel time 5 minutes round-trip



B I B L I O G R A P H Y

Eckman, William F. The Fire Department Water SupplyHandbook. Saddle Brook, NJ: Penn-Well Publishing,1994.Provides in-depth information on water supplies, espe-cially relay operations and tanker shuttle operations.

ISO Fire Suppression Rating Schedule. New York: Insur-ance Service Office, 1980.Water supply section provides information on howwater supplies affect rating.

Chapter

12PUMP DISCHARGE PRESSURE CALCULATIONS

Learning Objectives

Upon completion of this chapter, you should be able to:

Calculate pump discharge pressures for a variety of hose line configurations using the for-mula PDP = NP + FL + AFL + EL.

NFPA 1002Standard the Fire Apparatus Driver/Operator

Professional Qualifications(2003 Edition)

This chapter addresses parts of the following knowledge element within sections 5.2.1 and 5.2.2:

Hydraulic calculations for friction loss and flow using both written formulas and esti-mation methods.

The following knowledge element within section 5.2.4 is also addressed:

Calculation of pump discharge pressure.

318

Chapter 12 Pump Discharge Pressure Calculations 319

INTRODUCTION

In many respects, the sum total of this textbook boils down to this chapter: calcu-lating pump discharge pressures. Almost every point discussed in the text can belogically tracked to the point of flowing water from a nozzle. From driving the appa-ratus to preventive maintenance to operating the pump, the ultimate achievementof fire pump operations is providing the proper flow and pressure to a nozzle.

As stated in Chapter 11, the use of flow meters simplifies the process of firepump operations by eliminating the need to calculate friction loss. Pump opera-tors simply increase the pump speed until the correct gallons per minute for a noz-zle are indicated on the flow meter. In turn, the same flow is delivered to thenozzle. When supplied with the correct gpm, the nozzle, by design, automatical-ly develops its proper operating pressure. When pressure gauges are used, thepump operator provides the nozzle with the correct operating pressure. In turn, the design of the nozzle automatically ensures the correct gpm are flowing. Themajor difference between the use of pressure gauges and flow meters is the require-ment to calculate pressure changes within a hose configuration.

The focus of this chapter is on calculating pump discharge pressure. Thesample calculations begin with simple single lines and progress to more compli-cated multiple-line configurations. Friction loss constants and appliance frictionloss can be

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