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I have an underground cistern that has the typical set-up like a well. I have no problem when running the system(irrigation) and the pressure switch(40/60) cuts on and off fine. Overnight, even when not running the system, the pressure relief valve opens up and water drains out. The pressure shows 80psi and the relief valve opens at 75psi. Shouldn't the pressure switch keep that from happening or is is something else such as a problem with the pump.
Thanks.
Is the tank bladder still good, sounds like maybe a expansion when it gets warm. Are we talking a lot of water out of the relief or just a little?
About a pint of water. The tank seems fine and is hollow when I tap it. If I turn the power off, I do not have the problem.
Bladder style pressure tank? if so i would verify the bladder still holds its air charge.
i agree. It's likely not a pump or switch problem. Probably a failing pressure tank and the hot water tank heating causes the pressure to rise.