I’ve got an automatic fire suppression system in my garage. It was originally installed in 2003.
The pressure reducing valve (PRV) is required to be set at 100 minimum for this system.
Everything worked well from 2003 to 2011 when I noticed the system pressure was too high. I replaced the pressure reducing valve with the same unit, a Wilkins/Zurn 600XLHR. Designed to accommodate up to 300 inlet PSI, factory set at 85 PSI (adjustable from 75-125 PSI). It is important to note this PRV has a direct acting integral by-pass design prevents buildup of excessive system pressure caused by thermal expansion, typically from a water heater.
Recently I noticed the pressure had raised to 150 PSI and suspected the PRV had failed again after 12 years of service.
I replaced the PRV with the same model as the two before. Here is where the trouble began. After I installed the new PRV I adjusted the pressure to the recommended 100 PSI. The pressure held constant until the next day when it had risen to 150 PSI. I released the pressure in the system, then turned the water back on, adjusted the pressure down to 75 PSI and within a day (late afternoon) the pressure had risen to 150 PSI again.
I removed the newly installed PRV and exchanged it for a new unit (same model.) I reinstalled it but did not adjust the pressure, leaving it at the factory setting of 85 PSI.
Overnight the pressure held at 85 PSI. However, by 2:00 pm the next day the pressure had risen to 115 PSI.
I opened the main drain for 1 minute, purging the system. Once I closed the main drain the pressure stood at the factory setting of 85 PSI.
Does anyone have any idea what is going on? It is not particularly warm now, and I have not done anything to the system other than change out the PRVs.
Could the back flow preventer be the source of the problem? It is 19 years old. (Black Arrow in photo)
The system doesn’t have an expansion tank. Is there a PSI pressure that will activate the system?
Factory set at 85 PSI
