Relay Pumping Operations

May 17, 2010








Given information from discussion, handouts, and reading materials, explain the pump operator's responsibilities to pump a supply line, given the length and size of line, flow and desired intake pressure, so that adequate intake pressures and flows are provided to the next pumper in the relay. The student will perform to a written test accuracy of at least 70%, successfully complete the skills on a skills check-off list, and meet the job performance requirements of NFPA 1002 (1998).


Relay Pumping Operations

   • Relay Apparatus and Equipment

   • Relay Pumping Operational Considerations

   • Types of Relay Pumping Operations

   • General Guidelines for Relay Operations


SPO 1-1 Given information from discussion, handouts, and reading materials, explain the pump operator's responsibilities to pump a supply line, given the length and size of line, flow and desired intake pressure, so that adequate intake pressures and flows are provided to the next pumper in the relay. The student will perform to a written test accuracy of at least 70%, successfully complete the skills on a skills check-off list, and meet the job performance requirements of NFPA 1002 (1998).

EO 1-1 Determine what apparatus and equipment are required to design a relay. (NFPA 1002 (1998), 3-2.2, 6-2.2)

EO 1-2 Describe the various considerations associated with relay operations. (NFPA 1002 (1998), 3-2.2, 6-2.2)

EO 1-3 Describe the various types of relay operations. (NFPA 1002 (1998), 3-2.2, 6-2.2)

EO 1-4 Describe the basic operating guidelines for a relay. (NFPA 1002 (1998), 3-2.2, 6-2.2)


A. Relay operation uses pumper at water supply source to move water under pressure through one or more hoselines to next pumper in line

B. Source pumper boosts pressure to supply next pumper, and so on until water reaches fireground

C. Any apparatus equipped with sufficient fire pump placed in middle of relay to assist with pumping chores

D. Following terms used to describe various functions of apparatus in relay pumping operation

  1. Source pumper or supply pumper is pumper connected to water supply at beginning of relay


  2. Water supply fire hydrant or static water supply source

  3. Source pumper pumps water to next apparatus in line

  4. Relay pumper is pumper or pumpers connected within relay that receives water from source

      pumper or another relay pumper, boosts pressure, and supplies water to next relay pumper or

      attack pumper

  5. Attack pumper is pumper located at fire scene receiving water from relay and supplying attack lines

      and appliances

E. Fire departments use hose tenders to assist in hose lays associated with relay pumping operations

  1. Hose tenders may or may not equipped with fire pump

  2. Hose tenders carry mile or more of LDH

  3. Hose carried in traditional style hose bed or on large, mechanically operated reel

  4. Hose tenders carry wide assortment of relay valves, discharge manifolds, and other special water

      supply equipment used for relay pumping operations

F. Both 3-inch hose and LDH used for relay pumping operations

G. When 3-inch hose used for relay operations, two or three hoselines laid

H. Variety of hose and pump appliances used to assist with relay pumping operations

  1. Intake pressure relief valves or relay reliefs intended to reduce possibility of damage to pump and

     discharge hoselines caused by water hammer when valves closed too quickly or intake pressure

     rises dramatically

  2. Two basic kinds of intake pressure relief valves

      a. One type supplied by pump manufacturer and integral part of pump intake manifold

      b. Second type add-on device screwed onto pump intake connection

      c. Devices preset to allow set amount of pressure into fire pump

      d. If incoming pressure exceeds preset level; valve activates and dumps excess pressure/water until

          water entering pump at preset level

      e. Valves set within 10 psi of static pressure of water system supplying pumper or 10 psi above

         discharge pressure of previous pumper in relay

     f. Most screw-on intake pressure relief valves equipped with manual shut-off valve

     g. Bleeder valves on intake pressure relief valve allow air to be bled off as incoming supply hose


    h. Particularly important when using devices in conjunction with LDH

    i. Large amount of air pushed through hose until solid column of water reaches valve

   j. Bleeder valves located directly in intake piping to pump itself.

I. Relays dependent upon later-arriving companies set up initial relay of lesser volume and greater spacing with in-line relay valves in relay line for incoming pumpers

J. Valves allow late-arriving pumpers to hook up after relay operating and boost pressure (and corresponding volume) without interrupting operations

K. If LDH relay pumping operation intended to support more than one attack pumper, discharge manifold used to break down LDH into two or more hoselines then connected to attack pumpers


A. Relay operation based on two things

  1. Amount of water required at emergency scene

  2. Distance from emergency scene to water source

B. Relay must supply total water necessary to complete fire fighting operation

C. Relay used to supplement inadequate municipal water supply system

D. Amount of water needed to flow has major impact on design of relay

E. Longer relay distance, more hose necessary

F. More hose equates to more friction loss

G. Desirable to increase amount of flow through relay, one of three things necessary

  1. Increase size of hose or number of hoselines used in relay

  2. Increase pump discharge pressure of pumpers operating in relay

  3. Increase number of pumpers in relay

H. Generally impractical to shut down existing relay to replace hose being used with larger hose

I. Possible to have engine or hose tenders not already committed to pumping in relay to lay additional hoseline between relay pumpers

J. Each pumper may have additional hoseline attached to pump and begin flowing hose when all pumpers ready

K. Possible to have pumpers increase pump discharge pressure, not necessarily mean that volume of water through relay increased

L. Pumpers rated to pump maximum volume capacity at net pump discharge pressure of 150 psi

M. Depending on length of hose lay and volume of water being flowed, eventually get to point where increasing pressure will not increase volume

N. When considering increasing pressure, limited by pressure to which fire hose annually tested

  1. At no time should discharge pressures exceed maximum operating pressure for hose being used

  2. Hose pumped at pressures do not exceed 90 percent of annual service test pressure

O. Elevation pressure factor in relay pumping operations

  1. If relay operation pumping uphill, pressure loss on system greater than caused simply by friction


  2. Reverse true if operation going downhill

  3. Elevation pressure not affected by amount of water moved, only by topography

P. Increasing flow in relay accomplished by placing additional pumpers in relay

  1. By shortening length of hose each pumper has to supply, maximum pressures and flows maintained

      within hose assembly

  2. If in-line relay valves not placed in hose lay from outset, necessary to shut down relay when

      additional pumper(s) added

Q. In situations where low flow rates required and LDH available, required spacing between pumpers so great that exceeds amount of hose carried on each pumper

R. In cases may be necessary to call pumpers solely to lay hose but not actually participate in pumping process


A. Each fire department, or group of fire departments in particular region, should have SOP for type of relay pumping operation they will use

B. Agencies that have potential to work together on relay pumping operations should perform relays in training environment on regular basis

C. Some organizations have organized procedures for providing relay pumping capabilities at emergency scene

  1. When IC determines necessary to use relay to provide adequate amount of water to scene, relay

       task force or strike team requested

  2. Three to five pumpers dispatched to scene

  3. Companies come in and establish water supply independent of companies already operating on


D. Two basic designs for relay pumping operations: the maximum distance relay method and constant pressure relay method

E. Maximum Distance Relay Method

  1. Involves flowing predetermined volume of water for maximum distance pumped through particular

      hose lay

  2. By using table in Appendix A, operator can determine distance that certain flow pumped through

      hose carried on apparatus

  3. Built into figures in table is 20 psi residual pressure at next pumper in relay

  4. Figures in chart based on discharge pressure of 200 psi for 2½- and 3-inch hose and 185 psi for

      4- and 5-inch hose

  5. When considering distances in table in Appendix A, operator must keep in mind--all fire

      department pumpers rated to flow maximum volume at 150 psi, 70 percent of maximum volume at

      200 psi, and 50 percent of maximum volume at 250 psi

  6. Because table in Appendix A based on discharge pressures of 185 and 200 psi, following are

      minimum pump capacities used to achieve flows/distances on tables:

      a. 250 and 500 gpm flows: 750 gpm rated pumper

      b. 750 gpm flow: 1,250 gpm rated pumper

      c. 1,000 gpm flow: 1,500 gpm rated pumper

      d. 1,250 gpm: 1,750 gpm rated pumper

  7. If local procedure use distances less than those on chart, possible to use smaller capacity pumps

      than listed or remove one or more pumpers from relay

  8. Using figures in table in Appendix A, number of pumpers needed to relay given amount of water

      determined by using following formula:

Relay Distance + 1 = Total Number of Pumpers Needed

  Distance From

Appendix A

Note that when using formula, always need to round up to nearest whole number. For example, if answer 3.2, actually need four pumpers to achieve flow.


If single line of 3-inch hose used, how many pumpers needed to supply 1,000 gpm to fire scene 1,000 feet from water source? From table in Appendix A, can be seen that maximum distance water will flow at 1,000 gpm through 3-inch hose 225 feet. Divide figure into distance to fire, add 1 for attack pumper:

1,000 = 4.4 +1 = 5.4 or 6 pumpers needed



If two lines of 3-inch hose used, how many pumpers needed to supply 750 gpm to fire scene 2,000 feet from water source?

Find distance in table in Appendix A for two 3-inch inch hoses at 750 gpm

Then divide distance into total distance

2,000 = 1.25 + 1

1,600 = 2.25 or 3 pumpers needed

  9. When using method to establish relay, common sense used

  10. By checking tables, 750 gpm flowed for 1,600 feet through dual 3-inch hoses

  11. If distance to fire scene 2,000 feet away, place 1,600 feet between source pumper and relay

        pumper, with only 400 feet remaining between relay pumper and attack pumper

  12. Place relay pumper more toward middle of supply hose

  13. If engine companies with different sizes of supply hose on board, distances between pumpers

        varied accordingly

  14. For example, if several engine companies setting up 1,000 gpm relay using 5-inch hose, each

        pumper 2,050 feet apart

  15. If engine shows up with dual lay of 3-inch hose, it can participate as long as dual 3-inch lay limited

        to 900 feet

F. Constant Pressure Relay Method

  1. Second type of relay pumping operation is constant pressure relay

  2. Relay method establishes maximum flow available from particular relay setup by using constant

      pressure in system

  3. Constant pressure relay depends on consistent flow being provided on fireground

  4. Attack pumper can maintain flow by using open discharge or secured waste line to handle excess

      beyond flow being used in attack lines

  5. Relay using constant pressure has several advantages if operators properly trained in use

      a. Speeds relay activation

      b. Each operator knows exactly how much hose to lay out and how to pump it without awaiting


      c. Requires no complicated calculations

      d. Radio traffic and confusion between pump operators reduced

      e. Attack pumper operator able to govern fire lines with greater ease

      f. Operators only have to guide and adjust pressure to one constant figure

  6. Forming the Constant Pressure Relay

      a. Position attack pumper at fire

      b. IC makes size-up and determines quantity of water needed

      c. Initial attack made with water carried on pumper

      d. Position largest capacity pumper available at water source if possible

      e. Crew begins making necessary connections to water supply

      f. Lay out hose load from relay pumpers according to procedures used jurisdiction

      g. Always leave at least two sections of hose in reserve in hose bed in event hose failure occurs

        during operation

      h. Connect all supply lines to pumpers in relay

      i. Operator for each pumper, except source pumper open unused discharge gate if pump does not

         have relay relief valve which allows air from hoselines to escape

      j. Pump 175 psi from pumper at water source

      k. Operator at first relay pumper closes unused discharge gate once steady stream of water flows,

          then advance throttle until 175 psi developed

      l. Each successive operator follows same procedure

      m. Each operator sets pressure regulating device

      n. Attack pumper operator adjusts discharge pressure(s) to supply attack line (s)

     o. Maintain flow from attack pumper during temporary shutdowns by using one or more discharge

         gates as waste or dump lines

      p. Do not shut down attack lines unless absolutely necessary

      q. If hoseline bursts, open discharge gate on relay pumper before rupture to dump water until

          length replaced

       r. Lay additional hoselines between apparatus in relay if additional water needed on fireground

  7. Operators in constant pressure relay keep correcting pump discharge pressure to 175 psi until:

      a. Intake pressure from pressurized sources drops to 20 psi

      b. If intake pressure drops below 20 psi, danger that pump will go into cavitation

      c. Operating hand throttle does not result in increase in rpm

  8. Constant pressure of 175 psi modified as needed for:

      a. Variations in relay pumper spacing

      b. Severe elevation differences between source and fire

      c. Increases in needed fire flow

      d. LDH requires lower discharge pressure to supply same volume of water

  9. When increasing relay pressure, source pumper adjusted until desired pressure reached

  10. Each successive pumper similarly adjusted

  11. When decrease in flow required, attack pumper throttles down

  12. One way is by opening dump line to relieve excessive water

  13. Source pumper should discharge dump line back into water supply source

  14. Relay pumpers toward water source successively throttle down to desired pressure

  15. Water supply officer or IC must realize flow and pressure limitations of given relay setup and

        should not attempt to exceed capabilities of apparatus and hose


A. Basic guidelines for all relay pumping operations, regardless of type chosen

B. Operators familiar with guidelines to be successful in relay pumping operation

C. Putting Relay into Operation

  1. Operation always begins with source pumper

  2. Largest capacity pumper used at source

  3. If relay being supplied from draft, source pumper have to develop higher net pump discharge

      pressure than other pumpers in relay

  4. Higher net pump discharge pressure needed because relay pumpers will have residual pressure at

      intake to reduce amount of pressure needed from pump

  5. Important to remember that maximum capacity of relay determined by capacity of smallest pump

      and smallest hoseline used

  6. Once water supply established, source pumper opens uncapped discharge or allows water to

      waste through dump line until first relay pumper ready for water

  7. Failure to keep water through pump could result in loss of prime

  8. Discharge pressure built up to desired value by increasing throttle

  9. Dump line discharge valve slowly closed to keep from wasting all water from water supply

  10. Relay pumper waiting for water with dump line or discharge open and pump out of gear

  11. When both source pumper and relay pumper ready, discharge supplying hoseline on source 

        pumper opened while valve on dump line closed in coordinated action

  12. Discharge to supply line opened slowly to prevent sudden discharge into empty hoseline

  13. Water begins to move from source pumper to relay pumper

  14. As water fills line, air forced through pump and out open dump line of relay pumper

  15. When water comes out of dump line, pump on relay pumper engaged

  16. Another option to start relay, or at least fill hoselines, with water from apparatus water tank

  17. Works best on short relays using 3-incbh hose

  18. On long lays of LDH, may not be possible to completely fill hose between two pumpers

  19. Most desirable to maintain intake pressure of 20 to 30 psi

  20. If relay pumper receiving intake pressure greater than 50 psi, valve to dump line on relay pumper

        adjusted to limit residual to 50 psi maximum

  21. Pump discharge pressure increases as throttle setting on relay pumper increased; therefore, valve

       to dump line gated down to maintain 50 psi residual pressure

  22. If dump line allowed to flow unrestricted, friction loss would increase in hoseline from source

        pumper to point pump would go into cavitation

  23. Once pump discharge pressure on relay pumper reached desired pressure with water being

       discharged, portion of relay established and no further adjustments necessary

  24. When next relay pumper ready for water, same procedure followed

  25. First relay pumper opens discharge valve supplying next pumper while closing dump line on

        coordinated basis

  26. Next relay pumper allows water to discharge through dump line and follows same procedure used

        by first relay pumper receiving water from source pumper

  27. When water reaches attack pumper, operator bleed out air from supply line by opening bleeder

        valve on intake being used

  28. Intake valve on attack pumper opened and water supply established through relay

  29. When one attack line shut down, operator opens dump line to allow water to flow and prevent

        dangerous pressure buildup in relay

D. Operating the Relay

  1. Once relay in operation and water moving, pump operators set automatic pressure control devices

  2. Use of automatic pressure control devices essential when operating in relay due to cumulative

      nature of pressure increases when changes in flow occur

  3. Auxiliary cooler adjusted as necessary to maintain proper engine operating temperature over

      extended periods of time

  4. If pumper equipped with intake relief valve put in service

  5. If valve adjustable, set to discharge at 10 psi above static pressure of water system attached to or

     10 psi above discharge pressure of previous pumper in relay

  6. At no time should relief valve be set for higher amount than safe working pressure of hose

  7. At setting, valve not open and cause excessive fluctuations when minor changes in flow occur

  8. If attack pumper equipped with readily adjustable intake relief valve, set between 50 and 75 psi to

      establish stable operating condition for attack pumper

  9. If attack line shut down or amount of discharge changes, friction loss in supply line decreases and

      residual pressure increases

  10. Intake relief valve opens, allowing water to dump out of intake

  11. Flow through supply line and entire relay increases and pressures return to original settings

  12. Additional flow requirements by attack pumper reduces residual pressure and causes relief valve

        to close

  13. Dumping action stops, allowing pressure to again return to original setting

  14. Small variations in pressure not significant and no attempt made to maintain exact pressures

  15. As long as the intake pressure does not drop below 10 psi or increase above 100 psi, no action


  16. Changing pressure at any pumper in relay operation has effect on others

  17. Excessive changes result in constantly varying pressure throughout relay

  18. Takes long period of time for pressure change to actually occur in long relay

  19. Time delay often responsible for overcorrection errors that have negative effects for entire relay


  20. Effective relay operations require good communications

  21. Each unit in relay aware of actions of other units so operations coordinated properly

  22. When pumpers within sight of each other, hand signals used; in extreme cases, messengers on

        foot effective

  23. Where additional radio frequencies available, one channel dedicated to coordination of water

        supply operation

  24. Once water moving, minimum of communication required

  25. When units involved in relay equipped with incompatible radios, portable radios useful

  26. Radio equipped ambulances or utility units used to establish communications throughout relay

E. Shutting Down the Relay

  1. Relay operations shut down from fire scene first

  2. If source pumper shut down while rest of relay still operating, pumpers run out of water and

      cavitation can result

  3. Starting with attack pumper, each operator slowly decreases throttle, opens dump line, and takes

      pump out of gear

  4. Once all pumpers shut down, hose drained and readied for reloading


Relay Pumping Operations

   • Relay Apparatus and Equipment

   • Relay Pumping Operational Considerations

   • Types of Relay Pumping Operations

   • General Guidelines for Relay Operations

REMOTIVATION: Being able to effectively and efficiently relay water at the scene of a fire may make the difference between a good save and another foundation.

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