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Thread: Help Please, Thermal Expansion Control Valve

  1. #1
    DIY Junior Member
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    Default Help Please, Thermal Expansion Control Valve

    Hi,

    I love this forum and it has helped a lot. We have purchased a new house and I have had some problems with the hot water heater. It is a 2002 State Select Power vent. It was a REO and was winterized when we bought it so when we first fired it up the T&P was leaking. I replaced it and all was well...so I thought. Friday the Thermal Expansion Control Valve was not just dripping put trickling steadily, I replaced it but it has not stopped the problem. It is leaking quite a bit.

    Is this a pressure problem or is it because the hot water heater is set to high? Do we need an expansion tank?

    Thanks so much.
    Last edited by rhumbaclave; 11-16-2009 at 06:26 AM. Reason: Completely messed up the description. It was a T&P leaking not a preasure relief.

  2. #2
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    If you have a PRV you need an expansion tank.

    John

  3. #3
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    Thanks John. I just realized I messed up my definitions. It was my T&P leaking not a PRV, I do not have a PRV. Sorry.

  4. #4
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by rhumbaclave View Post
    Thanks John. I just realized I messed up my definitions. It was my T&P leaking not a PRV, I do not have a PRV. Sorry.

    Just to further muddy the waters: PRV for plumbing is not the same as PRV for industry/process engineering. PRV typically referrs to a pressure relief valve, but for home plumbing it refers to a pressure regulating valve. The T&P is both a thermal and pressure relief valve.

    There is probably nothing wrong with the PRV. This is a thermal expansion problem and will require a small thermal expansion tank. Otherwise, the T&P will relieve everytime the system pressure hits 150. You can put a $10 test gauge on a hose bib or other tap to confirm the cycle.

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