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Jockey Pump Sizing & Requirements in Firefighting - NFPA 20

What is a Jockey Pump?

A jockey pump, also know as a pressure maintenance pump, maintains the pressure in the fire sprinkler system to avoid non-emergency starting of the main fire pump.

This keeps the main fire pump from short cycling, which shortens its life span. The jockey pump is designed to start before the main fire pump and return the fire protection system to its minimum static pressure. However, it is not designed to keep up with the system demand in regard to flow. In this case, the system pressure will continue to decrease until the main fire pump starts.

Requirements for the Jockey Pump.

  • Jockey pump is preferred to be of centrifugal type pumps.
  • Jockey pump shall be approved but shall not be required to be listed.
  • The controller for a jockey pump shall be listed but shall not be required to be listed for fire pump service.
  • The jockey pump shall not be required to have alternate or standby power.

Sensing Line:

The jockey pump shall have its own pressure sensing line of 15mm diameter nominal size made between its isolation valve and discharge check.

Jockey Pump Sizing:

The jockey pump should be sized to replenish the pressure of the fire protection system due to the allowable leakage and normal pressure drop in the pressure and it should have sufficient pressure discharge to maintain the desired fire protection system pressure as follows,

1 - For Situation Where the Jockey Pump Serves above Ground Piping for Fire Sprinkler & Standpipe Systems:

The jockey pump should be sized to provide a flow less than a single fire sprinkler. The main fire pump should start and run (providing a pump running signal) for any water flow situation where a sprinkler has opened, which will not happen if the pressure maintenance pump is too large.

2 - For Situation Where the Jockey Pump Serves Underground Mains:

NFPA 24 permits the underground mains to have some leakage, one guideline that has been successfully used to size pressure maintenance pumps is to select a pump that will make up the allowable leakage rate in 10 minutes or 1 GPM, whichever is larger.
A rule of thumb  for sizing jockey pump supplying underground piping is to use 1% of the fire pump rated capacity.

For example:

A fire pump with rated capacity of 2500 GPM.
Then the jockey pump flow rate is 2500 GPM x 1% = 15 GPM.

Jockey Pump Head:

Pressure of jockey pump shall be greater than the pressure of main fire pump by minimum of 10 psi to avoid false starting of main fire pump.

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