Issue with new water heater

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Mayers, Mar 20, 2017.

  1. Mayers

    Mayers New Member

    Joined:
    Sep 16, 2015
    Location:
    North Versailles, Pennsylvania
    Hello everyone,

    I recently installed a new electric water heater. The pressure relief valve keeps popping off non stop within seconds of water starting to fill the tank. Please note there is no expansion tank installed and there is no pressure reducing valve installed on the plumbing system. Also no back flow device.

    I checked the pressure coming into the house and it's averaging around 130 to 140 PSI. My understanding is this is high and a pressure reducing valve would fix this. Would this also be the reason the pressure relief valve on the water heater is popping or could it have shipped with a bad pressure relief valve?

    Should I go with an expansion tank first or the pressure reducing valve?
     
  2. Smooky

    Smooky In the Trades

    Joined:
    Apr 4, 2011
    Location:
    North Carolina
    Most T&P valves are designed to open at 150 psi. If it is opening at a pressure lower than that, it could be a faulty valve. The pressure is very high so I would recommend installing a pressure regulator and expansion tank.
     
    Last edited: Mar 20, 2017
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  4. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    No home should have pressure above 80 PSI.
    You will need a PRV there.
    Pressure Reducing Valve.
     
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  5. dj2

    dj2 In the Trades

    Joined:
    Aug 13, 2013
    Location:
    California
    Quote: "Should I go with an expansion tank first or the pressure reducing valve?"

    You want to stabilize and reduce your in house pressure to between 50 and 80 first.
     
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  6. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    The PRV goes first, and the thermal expansion tank goes farther in. The tank is often placed near the water heater.
     
  7. Mayers

    Mayers New Member

    Joined:
    Sep 16, 2015
    Location:
    North Versailles, Pennsylvania
    Thank you very much for your replies. I'll go home depot in the morning and get the PRV and expansion tank. :)

    BTW my understanding is most PRV have a built-in backflow device? Is this correct?
     
  8. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Those with "bypass" in the name or description do not. Others normally do.
     
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  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    If a PRV has a bypass valve, it won't open until the home pressure exceeds the supply pressure, which, kind of defeats the purpose of a PRV to keep the pressure stable. Without an ET, the pressure will cycle high enough to either return via a bypass, if present and working, or get high enough to cause the safety T&P valve to open.

    While you may not have installed a check valve or had a PRV, it is quite possible that the utility company may have installed one in the line to your house. This is done to help protect their supply in case some pollution might try to push back into their system. IOW, a bypass may not work, since many utility companies are installing check valves, or will be as they get around to upgrading things. You should not rely on a bypass in a PRV to do much of anything.
     
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  10. Mayers

    Mayers New Member

    Joined:
    Sep 16, 2015
    Location:
    North Versailles, Pennsylvania
    Just an update,

    I bought and installed everything this morning. No more issues :). Thanks everyone for your help.
     
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