Relay Pumping: Firefighting Strategy

Relay Pumping Overview

• Relay pumping involves using two or more pumpers in series to move water over a distance
• Water flows from one pumper through hoses to the next, reaching the fireground for attack lines
• Engine positioning in the relay line depends on the fire and water source locations and the availability of roadways and room to maneuver

Standardized Procedures

• A generalized procedure is recommended but might not have all pumpers at the same engine pressure
• Without a standardized relay procedure, confusion, time loss, and inadequate water supply can occur
• Adjustments can be made after water flow has started
• Excessively long stretches (over 1000 feet) usually require relaying to combat friction loss while maintaining adequate water flow

Planning

• Company preplanning is important to determine locations where such operations are required
• These can be implemented as pumpers arrive instead of arranging already placed companies

Examples of Relay locations

• Extra-alarm fires with residual water supply exhausted
• Areas distant from water main terminations
• Major fires on expressways or bridges where water supply is distant
• Areas with insufficient water supply due to construction or breaks in the water main system
• Large complexes or areas with limited hydrants such as airports, refineries, and junkyards
• Areas requiring drafting from a site remote from the fireground

Equipment

• The Philadelphia Fire Department equips all Engine companies and reserve apparatus with 1500 GPM pumpers and 1000 feet of LDH supply lines

Water Supply Strategy

• The water supply choice directly affects water delivery to the emergency
• The pumper connected to the water supply is the source pumper
• The source pumper should be connected to either a green or red top hydrant
• The last pumper at the incident is the fireground pumper
• Specialized apparatus like Squrt or Foam pumpers should be used as the fireground pumper to maintain company versatility

Relay Pumper Designations

• Pumpers between the source and fireground pumpers are relay pumpers
• It may be useful to designate relay pumpers in order like "Relay Pumper 1", "Relay Pumper 2", so on
• This is useful for clarity during communications, especially over long distances, when actions must occur in sequence

Pumper Spacing

• Recommended stretch between pumpers is 500' to 900'
• Less than 500' provides sufficient residual pressure for one pumper
• A 900' maximum stretch allows replacement of a burst length with a 100' reserve line and a 5" soft-suction
• Adequate water from source to destination determines the necessary number of relay pumpers
• Stretches can be accomplished through forward, reverse, or manual lay, and the fireground pumper maintains a fireground hose load

Relay setup

• Each pumper in a relay, except the source pumper when operating from a positive pressure source like a hydrant, extends a 50' length of 3" hose from an unused discharge gate
• The open end is secured to prevents uncontrolled movement
• The dump/discharge line can bleed off trapped air and maintain water flow during shutdowns between the pumper and fireground nozzles
• The dump discharge line should allow unimpeded water flow, not hinder firefighting, compromise ground stability, or allow ice accumulation
• Set relief valves on all relay pumpers to the appropriate discharge pressure

Operational Notes

• Pumper staging valves must be in volume
• Pumpers with faulty staging valves that can't switch to volume should not be used

Estimating Distance

• Philadelphia city blocks average 600 feet, but Northeast and Northwest blocks average 700-800 feet
• One relay pumper can typically cover 1 to 1 ½ city blocks
• Utility poles, typically placed 120 feet apart, can help measure distance in non-urban areas

Calculating Pumpers

• The formula for pumpers needed is: # of pumpers = distance in feet / 900 feet + 1
• Round up the answer if it's not a whole number

Relay Charging Protocols

• Before starting the relay, all companies notify the source pumper they're set up and ready
• The source pumper operator notifies the next pumper that its intake is being charged, signaling that pumping has begun for all pumpers
• The source pumper operator sets an initial pressure of 50 PSI on the discharge line to the next pumper

Pressure management

• The receiving intermediate relay pump operator or fireground pump operator opens their dump/discharge line to relieve trapped air
• After obtaining full water flow, this pump operator shuts the dump/discharge line and opens the 5" discharge line to the next pumper
• The sending pump operator sets an initial pressure of 50 PSI on the discharge line and notifies the next company to charge its intake
• Each pump operator opens the dump/discharge line to expel trapped air and follows the initial pressure and radio notification procedure until the fireground pumper gets water

Fine Tuning

• The fireground pumper operator notifies the source pump operator to raise the discharge to 125 PSI
• Once the pumpers are discharging, the pump operator must keep their discharge gates fully opened
• Pump operators watch their discharge gauge and smoothly adjust their throttle when the next pumper starts taking water to restore the 150 PSI discharge pressure
• Maintain a minimum compound gauge pressure of 5 PSI for the source pumper, or 20 PSI for an intermediate relay pumper

Operational Caveats

• Avoid overreacting to small pressure variations
• No action is required unless intake pressure drops below 20 PSI or exceeds 100 PSI
• Any pressure change by any pumper affects the others
• Set all pumpers' relief valves

Automatic Pressure Control

• The use of automatic pressure control devices is essential because of cumulative pressure increases

Communication

• Good radio communication is crucial
• All units in a relay should know which units are in their relay
• Pump operators must constantly monitor radio to avoid delays

Standardized Communication

• Standard radio terms are vital during shutdown
• "Raise" or "lower" indicate pressure changes

Relay Pressure Considerations

• Discharge pressure can be increased, if necessary, and is based on the usable residual intake pressure at the source pumper
• The minimum intake pressure on the source pumper (5 PSI) and intermediate relay pumpers (20 PSI) still remains and dictates if discharge pressure can be increased
• An increase in relay discharge pressure should be considered only if the source pumper's intake pressure is above 5 PSI while discharging at 125 PSI for 5" lines, unless the water supply is supplemented
• An increase must start at the source pumper and work up the line

Hose and Capacity

• 5" line procedures, with 800'-900' stretches between pumpers will approximates pump capacity relay at approximately 1500gpm
• Maximum discharge pressure for 5" line companies in a relay is 175 PSI

Strategic Considerations

• Fireground commanders and officers must know the limitations of the relay when deciding which master streams and firefighting lines can be used

Relay Shutdown Protocol

• Relay operations should be shut down from the fire scene first to prevent pumpers from running out of water and cavitating

Relay Shutdown Steps

• The fireground pump operator throttles down the discharge lines and opens the dump/discharge line to maintain water flow
• The pump operator notifies the source pumper that the relay is shutting down, also notifying all others in the relay
• All companies must confirm they received shutdown message
• If a pumper doesn't respond within one minute, repeat the radio contact attempt

Water Flow Considerations

• Involved pumpers throttle down their discharges completely and open their dump-discharge lines
• Once a company's dump-discharge is opened, the pump operator shuts down their discharge gate completely and takes the apparatus out of pump

Additional Shutdown Notes

• This flow must not be cut off at any point between the fireground nozzles and the source pumper, unless under emergency conditions

Procedures for Burst Hose Length

• Notifying all pumpers and the fireground commander that the relay must stop to change hose lengths as soon as a burst is discovered
• Ensure all operators in the relay acknowledge the radio message
• All pump operators in the relay immediately throttle down their pumps, open the dump valve, and shut down completely, followed by confirmation of message received

Operational Pressure Management

• Isolate water flow or relieve pressure through the dump/discharge
• Closing the fireground nozzles requires their operator to relieve pressure
• A marked pressure increase is inevitable when a nozzle from the fireground pumper is closed when the stretch is properly set, and is more severe with more pumpers in the relay

Relay Pumping Summary

• Always use a green or red top hydrant
• Ensure that fireground pumpers maintain its full hose load for use with fireground operations
• Relay pumpers can extend to a maximum length of 900 feet, and a shorter stretch of 500 feet minimum
• Ensure a minimum of one length of 5" hose line, and accompanying soft suction lengths, is maintained on each apparatus to cover burst length operations
• All pumpers, except the source pumper must be installed with a 50 foot length of 3" hose, and secured so that it operates as a dump/discharge line
• Relief valves must be set to the appropriate discharge pressure, and staging valves must be in volume
• Only Squrts and Foam pumpers may be used as fireground pumpers
• Be sure to notify the source pumper that the relays are set up and ready to pump
• Pumpers should target 50 PSI at the beginning of the relay
• It is recommended to push 125 PSI at a length of 800-900 feet, up to a maximum of 175 PSI
• Source pumpers should maintain a minimum compound gauge reading of 5 PSI, and intermediate relay pumpers should maintain a minimum of 20 PSI
• Unless the pumpers are the source, the intake pressures should not exceed 100 PSI
• Maintain close radio contact
• Increase relay discharges only when source pumpers see an excess of 5PSI for the minimum Recommend a discharge incremental increase of 25 PSI for 5" lines relays
• Pressure increases must always start at the source
• When shutting down a relay, always perform in order from the fireground pumper
• Once water is moving in the relay, do not shut down at any point under non-emergency conditions
• The pumps intake and discharge lining must be secured with rope hose tools