The water distribution system has a fire pump house on it. When a fire suppression system has waterflow, the fire pumps start up to boost the system pressure from 50 psi to 115 psi to meet flow requirements. When the pump is shut down/offs, the system returns to 50 psi, leaving 115 psi trapped above the alarm checks and 50 psi below on the supply side. Topside clapper 115/50 bottom side clapper a difference of 65 psi.
Problem: On the large wetpipe systems, it take 4 to 7 minutes before equilibrium is achieved and waterflow occurs. This of course is unacceptable since waterflow should happen in less than 5 minutes and alarms within 90 secs. The pumps are started by the flow switch located on the riser above the alarm check. There must be a 66 psi drop on the system side before waterflow occurs, to activate the flow switch which starts the pumps and alarms.
Solution: I an thinking of installing a pressure switch, to start the pumps, when there is pressure loss on the topside of the alarm check. The pumps will increase supply pressure, eliminating the 65 psi difference, allowing a quicker response on the clapper and alarms. Would it work? Is it a legitimate solution?