Water pressure doubles overnight.
Hi all... I'm new here. I found this forum by Googling plumbing help so hopefully someone could point me in the right direction to my issue.
My house is on city water and has an electric hot water heater that holds 74 gallons. I installed an expansion tank recently because my pipes started to hammer. My static water pressure is 40 lbs in the house and I've set the expansion tank to 40 as well.
If no water is being used for an hour or more, my pressure will rise to about 50 lbs according to my gauge that is hooked up to a cold water line. I thought that having an expansion tank would equalize the pressure to keep it at 40 but doesn't seem to be working like that for me. A 10 lbs rise in pressure doesn't seem that bad but overnight that sucker will rise to 80 lbs.
The expansion tank I installed is an Amtrol ST-12 and my water temperature is about 115-120 degrees.
What am I missing here? I don't notice any hammering but the rise in pressure does concern me. Unfortunately, I didn't measure overnight pressures before installing the expansion tank.
Thanks in advance for any suggestions you guys might have.
Last edited by alphamabox; 03-20-2017 at 04:14 PM.