T&P valve releases after high usage

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    • #274644
      Avatar photoAnonymous

        Here is my problem…I put a new 50gal direct vent State water heater in. Had a problem with relief valve firing when usage was high. Found high pressure (120lbs after relieving any thermal expansion) and replaced water regulator; set to 68lbs incoming pressure. Watched guage as tank recovered after two showers and pressure was 110lbs peak…due to thermal expansion. Water temp is 138 Farenheit at peak after recovery complete. Why after high usage…usually on Sat. when wife does lots of laundry, dishes etc. does this leak? I have a pressure guage screwed onto basin faucet for the duration of this quandry. P.S.- Had new thermostat on tank installed first…jumped too quick!! –Currently have istalled 175lb T&P waiting for next weekend…think it might be more a temp thing??? Any takers? (please)

      • #290087
        Avatar photoSylvanLMP

          Rather then replacing the “Normal” 150# T&P with a 175 type I think you should double check your expansion tank for size and proper expansion of the bladder. Increasing the relief valve pressure will cause a lot of thermo stress on your tank and premature failure.

          Is your water supply city or well and possibly too much air in the system.

          Air can compress and this would cause the T&P to do it job.

          Your temperature rating of the 3/4″ T&P should be 210 deg F.

          Have this system checked by a Licensed Master plumber to be sure it is safe. Good Luck

        • #290088
          Avatar photomojo-13

            I have a public water supply and I have no Expansion tank at all.
            I was merely refering to the difference in pressure in the system between relieved and thermal expansion due to heating of the tank with no water being run during the recovery period. I considerd adding a tank, but the pressure does not exceed 110#’s.
            I am going to install a new 150# T&P and hope that the temperature probe is defective…otherwise I have a problem with the tank overheating on a large recovery period…is there a duration adjustment for the flame? Wouldn’t a thermostat shut down the gas after reaching the 138 or so setting? I have reduced the thermostat slightly as well. Thanks for taking a shot at this one!!! anything else that you think might help is welcomed and appreciated!

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