So, when should a fire pump be replaced? If an owner of a fire pump is testing and maintaining the equipment based on NFPA 25, then the answer to this question is often based on the hydraulic performance of the pump in question. The pump is tested, and perhaps it failed a flow test. For example, if the pump is rated 1000 gpm @ 100 psi boost, and upon evaluation of the performance test results the pump is now only providing 1000 gpm @ 93 psi boost, then the fire pump might need to be replaced based on this performance deficiency alone.