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Hi I m changing out my 33 gal pressure tank to a 44 gal. Instructions say I need a pressure relief valve but I don’t have one on original set up so my shallow jet pump pressure switch is set at 20/40. Should I install a pressure relief valve?

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    Have almost the same setup as you, no relief valve. Did have the pressure switch stick on(did not turn off) once and the pressure went close to 100 pounds. A pressure relief valve is cheap insurance.
    – crip659
    Jul 30, 2022 at 0:15
  • @crip659 How did you know the switch stuck on? I assume the water came out of the faucets at an alarming rate, but I've never seen this before and as a new person to having a well I thought I'd ask.
    – RetiredATC
    Jul 30, 2022 at 1:20
  • Hi yes sir cheap insurance, it never occurred to me I will install one now thanks guys !!! Jul 30, 2022 at 2:29
  • @RetiredATC It only happen once in 40 years. Pressure was high at the faucets and developed a few leaks at pipe joints. Having a spare pressure switch comes in handy, since they wear out.
    – crip659
    Jul 30, 2022 at 9:50
  • @crip659 Could you please explain how a pressure regulator would fit into the water system? Would it be mounted just after the tank? Is there a way that you could tell that the well pressure switch was stuck open if you had a pressure regulator?
    – RetiredATC
    Jul 30, 2022 at 17:15

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A pressure relief valve is required to protect from a condition where the pressure switch fails to shut the pump off. It should be of a value well above the normal pressure in the house, and well below the pressure rating of the tank - the tank folks require one because when the pressure tank is over-pressurized, it becomes an explosion hazard. Under normal operation conditions, it should never actuate. It's not for normal operating conditions. It's a safety device for abnormal conditions.

Most domestic systems operate at 80 PSI or below, and most tanks are rated for more than 100 PSI, so a 100PSI relief valve is fairly commonly available. With a 40 PSI cut out you could use a lower pressure relief valve, like 75 PSI, but one might be somewhat more difficult (certainly not impossible) to find. So long as your tank is rated for MORE than the relief valve, it will do the important job.

Depending on your particular pump you might handwave about the pump not being able to pump that high (if it can't) but the valve is cheap insurance, and if the pump got replaced with a different one...

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  • Water is not an explosion hazard this is why they use water to test pressure tanks to aprox 5/3 working pressure for hydrostatic testing. If they split the pressure is gone because water is not a compressible like air.
    – Ed Beal
    Jul 31, 2022 at 2:22
  • @EdBeal A well pressure tank is air over water, and the air is the part that makes "explosion" a problem here, same as it is for an air compressor tank.
    – Ecnerwal
    Jul 31, 2022 at 2:24
  • It is a fixed bladder of limited volume the pressure set at or within 2 psi of the low pressure cut in let’s get crazy and put it at 80 still at max compression 120 there is only 120 psi of air how many well pumps can produce more than that water pressure ? small volume pressure tanks don’t even require hydrostatic testing (under 2” in diameter) even at high pressures +2000 psi so I don’t see a real explosion issue. And yes I have had tanks rust and split they just peed.
    – Ed Beal
    Jul 31, 2022 at 7:11

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