Just had the PRV changed at our house. Pressure coming into house before PRV is 160. Back of house around 55 to 60. My concern is that a couple of times a day it will spike to 75 - 80 for no apparent reason. It then settles back down to around 55. Today we were gone for 5 or 6 hours, no one else at home and the pressure was at 75, it peaked while gone to 85. Never came back to 55 until I flushed a toilet. I left the pressure gauge on to monitor.

Is this thing working correctly. It's 4 days old.

Thanks

water heater firing up, and heated water is expanding?
be happy the pressure does not drop as that would indicate a leak...

If it goes up overnight when no one is using the hot water, that would indicate that it is not operating properly.

unless the last water used at night was hot water such as someone taking a shower.

Just checked and there was no air pressure in the expansion tank, no water coming out of the schrader valve either. Pumped it up to 45#. I can see on the pump that air is in when I removed the pump to check again, no air. Went through this several times, same result. The unit is a Watts PET 5. Now what?



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You need a thermal expansion tank added to the system. It is evident you don't have one if you have pressure spikes after installing a prv. The prv closes the system and and when the volume of a system is constant, temperature increases cause a pressure increase. Since you need to alleviate the pressure, you can either eliminate the temperature change, or you can install a thermal expansion tank to increase the volume when the pressure exceeds the pressure in the tank. Or never use hot water again.

I have an expansion tank.

I spoke with Watts this morning(after I posted) and they said to remove the tank and then fill with air. Tank is filled with water and something about negative pressure in a closed system. The bladder could have drained gradually over time.



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make sure to charge the tank to 5 psi over gauge pressure when you open a faucet, then close it. That way any excess pressure is relieved.

YOU cannot "pressurize" the tank with air, unless you either turn off the water and drain the system or remove the tank from the piping.