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  1. #1
    Join Date
    Jun 2008
    Posts
    1

    Default Water Pressure Spike

    We recently install a new PRV and checked it with a gauge by placing it after the PRV. The gauge is reading 58 psi with a spike of 120. Do we need to be worried about the spike? The 58 psi is without any water running.
    Last edited by pearbull; 06-08-2008 at 02:29 PM. Reason: typo

  2. #2
    Join Date
    Aug 2007
    Posts
    1,131

    Default Re: Water Pressure Spike

    When do you see this 120# spike?

    Is it perhaps a little while after running some hot water? (As in.....after you've used enough hot water to cause the water heater to kick in.)

  3. #3
    Join Date
    Feb 2008
    Location
    Nashville, TN
    Posts
    149

    Default Re: Water Pressure Spike

    You should not get any kind of spike with a properly installed PRV. That is what is does. Pressure Reducing Valve. 58 psi is ok. But, 120 psi is crazy. Also, the guage should be installed in the line, so as you turn up or down the PRV you can see what pressure you are getting (have the water running through). Process of elimination. Good luck.

  4. #4
    Join Date
    Aug 2007
    Posts
    1,131

    Default Re: Water Pressure Spike

    Pressure spikes of 120 psi are not at all uncommon after installing a PRV...........*if* a PRV was installed which does not have a high pressure bypass to relieve back into the city water line....or if the city has a check valve on their side that prohibits backfeeding.

    When hot water is used, it is replaced with cold water.....and eventually the WH kicks in. The cold water in the WH tank is then heated.....and expands. If that expanding water does not have an escape route (all water usage has ceased and relief back into the city supply is prohibited)..... the line pressure increases. This is what expansion tanks are for.

    If the increased pressure from heating the water gets high enough ....it will/should theoretically relieve itself (to some degree) from the T&P valve on the WH..............*if* the T&P is working properly. I'd recommend installing an expansion tank instead.
    Last edited by goldhiller; 06-12-2008 at 09:56 PM.

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