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Thread: High water pressure

  1. #1
    DIY Junior Member
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    Sep 2007
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    Default High water pressure

    Hello,

    I have a house in a neighbourhood with very high water pressure 100+psi.
    A pressure reducing valve was installed and appears to work once there is water flowing,
    this was tested at various settings and looking at the gauge.

    However when there is no water used in the house/flowing, the pressure rises to the 100+psi.
    Are PRV valves supposed to work like this or is there a problem with this valve ?

    Thanks,

    L

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
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    Default

    The PRV limits pressure coming into the house. If the pressure is building from the water heater, the PRV is not at fault. Do you have a working expansion tank?

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    Default

    WIth a PRV, you need a working expansion tank so the WH operation which causes the water to expand when it works, has someplace to go. If that isn't the reason for the pressure rising, then the PRV is defective and needs to be replaced or rebuilt. It could be letting pressure rise because of a bad internal seal, dirt, or other defect.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    DIY Junior Member
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    Default

    yes, there is no expansion tank, should I just have one installed nearest to the cold input of the water heater ?
    Also are expansion tanks the same as water pump pressure tanks ?

  5. #5
    DIY Junior Member
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    Default

    I ran some tests tonight with a pressure gauge, both with the water heater on and off.
    The heater is not the problem as the pressure creeped up to max on the gauge.
    Good thing is that the mains is split into two -
    one for a tank supply which feeds a pump in case water mains supply is off
    and secondly into the house via the PRV.
    I removed the PRV and shut off that supply, I think I am going to leave it that way and have one less
    thing to go bad and just run the house off the pump supply and let the float valves in the tanks take the high pressure instead.

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