Why/When Required:
To start with, technically you are not required to provide a jockey pump on all systems. NFPA 20 section A.4.25 states "Pressure maintenance (jockey or make-up) pumps should be used where it is desirable to maintain a uniform or relatively high pressure on the fire protection system." The goal is to not shock the system with water hammer when the main fire pump starts. You don't want to be boosting the pressure from 10 psi to 150 psi. You want to be boosting the pressure in the 5-15 psi range.Jockey Pump Types:
Jockey pumps are not required to be listed per NFPA 20-2010 section 4.25.1. The failure of a jockey pump results in the main fire pump which would be considered a success.Sizing of Jockey Pumps
GPM Rating - Aboveground Only Systems
NFPA 20-2016 section 4.26 states the pump "shall be sized to replenish the fire protection system pressure due to allowable leakage and normal drops in pressure". The appendix language goes on to state "... The main fire pump should start and run (providing a pump running signal) for any waterflow situation where a sprinkler has opened, which will not happen if the pressure maintenance pump is too large. "
GPM Rating - Large Underground Systems
where:L = testing allowance (makeup water), in gallons per hourS = length of pipe tested, feetD = nominal diameter of the pipe, in inchesP = average test pressure during the hydrostatic test, in pounds per square inch (gauge)
Assuming that you have a system that will not exceed 150 PSI in static pressure, the underground will need to be tested to 200 PSI.
- 500-feet of 6-inch Class 52 Ductile Underground (D = 6.280")
- Hydrostatic test pressure of 200 psi
- Allowable Leakage L = 0.30 gpm
PSI Rating - All Systems
- Flow rate to keep up with expected system leakage
- Maximum expected churn (no-flow) pressure so as to not exceed system rated pressure
- Adjust controller setpoints so the jockey pump turns off (bad idea for a variety of reasons)
- Provide a pressure relief valve to accommodate over pressurization (subject to human error and potential mechanical failure)
- Select a pump with a churn pressure (+ suction pressure) that won't exceed you system rating