Hot-Water Heater Pressure Relief Valve

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    • #277458

        I have my Heater set at about 120 degrees. Recently, the relief valve has started dripping when the heater comes on to heat the water. I tried replacing the valve (twice), but I’m still having the same problem. Any ideas?

      • #296295
        Avatar photoAKPlumber

          There could be a few reasons why.
          Sometimes an improperly installed or defective backflow preventer can block thermal expansion, leading to the TP valve’s opening. Could also be a pressure reducing valve somewhere.
          An expansion tank may help alleviate this problem.

        • #296296
          Avatar photoRetired plbg1

            Like AK said you might need and expansion tank, which most heater Co. tell you to install one. These guys give you a cheap price to put in heater and dont say anything about tank to keeop price down. Go to and ask for details on expansion tank for Residential WH.

            Art retired plbg

          • #296297
            Avatar photoSelgas

              To answer the question in simple terms I would advise the following : When water is heated it expands and unless there is an expansion tank in the system the only place the water can expand freely to is the Temperature, Pressure Relief Valve (TPRV). Without this device working the water can superheat and the whole tank could become a time bomb under tremendous pressure and no body wants that huh?
              To correct the problem you have there may require an inspection of the plumbing pipework to establish the best way to overcome the problem – have a chat with your local Plumber to get an idea of likely costs.

              Selgas Services Ltd
              Craftsman Gasfitters, Plumbers, Electrical Service Technicians

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