You need to either install a rebuild kit to your PRV, or replace it.
Most of the time, we replace the PRV, mainly because we can do that in one trip. You could look up the tag on your unit and see if parts are available.
I have major water pressure creep all the time. New water heater installed with expansion tank and the pressure is being relieved by the pressure release valve. I have tested the lines with a pressure gauge and the flow is regulated at 40-50 psi when running. The gauge registers a high of 150 psi over night which triggers the release valve. I have tested the line with the water heater turned off so I know it's not thermal expansion. My question, is the pressure regulator valve on the incoming line supposed to shut off the inlet when the line pressure reaches the set psi at say 50 or do they usually allow the pressure to continue? Do I need a different valve to keep out the higher pressure? I am the last house at the end of the street and I believe the water main ends here and does not continue. Not sure if the pressure regulator valve is bad as it does regulate when running. Thanks for the help.
It's kind of unusual for the supply pressure to be in excess of 150psi, but it can happen if you're close to the pump or water tower, or sitting at the bottom of a big hill. But, if it is, check the specs on the PRV you are using. Most can handle that pressure differential, but some might require a second one in series to drop the pressure incrementally. Have you measured your supply pressure?
To check and adjust the expansion tank, you must turn the water off, open a faucet to relieve any pressure, then you can check and adjust the pressure in the ET, otherwise, you are just checking the water pressure in the system.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014
I do know that 150 psi will test your plumbing for weak points.
It will also check Appliances and water fill valves.
I would kill water when not at home, until you can get it fixed. That should be ASAP.
Regulators go bad every once in a while. If you know how to fix them and have the time to do it, call the manufacturer for a kit. Otherwise, replace it, which is quicker and I bet cheaper.
Like was said before, if you leave the house, shut the water. You don't want to come home to a flood.
How fast does your water pressure creep up? You maybe able to work around this for a few days by opening a cold water tap to a veryslow trickle until you get the repair.
Pressure creeps up pretty fast when it isn't being used, the 150psi is only what I gauged it at before the relief valve worked, it could be more. No leaks anywhere else at that pressure.