I have new cottage with 3/4hp jet pump as the main source of water. 40 gallon water heater. When we leave the cottage the pump and water heater are tuned off. Both are turned back on when we return. For the 1st year after installation all was OK.
Now,when the pump and water heater are turned back on, as the water heats up the PRV opens and I water (a lot). If I turn off the water heater and the in-coming valve (cold water)for 30 mintes or so it seems to clear up. Sometimes I have to repreat this process. I have reduced the pump pressure to minimum and problem persists.
Any suggestions? After some research I am beginning to think an expansion tank may be the answer.