Pressure Reducing Valve concern

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by DRG32, Nov 26, 2012.

  1. DRG32

    DRG32 New Member

    Messages:
    5
    Location:
    Texas
    I recently had a pressure reducing valve installed to fix our 105 psi static pressure. We also had an expansion tank installed, and it is the appropriate size for our two hot water heaters. I adjusted the PRV to about 60 psi, and I have noticed the pressure will climb to about 65 psi after someone uses the shower, bath, and some other times throughout the day. The pressure immediately drops back to the desired setting of about 60 psi when a faucet is briefly used, and the pressure tends to hang right around 60 psi for the most part. The instructions state that this is natural and that it may happen when the water heater runs. It also states that a pressure relief valve or expansion tank must be installed, but they will not prevent a pressure rise, but should limit it to a safe level. I understand the need for the expansion tank with the now closed system, but is this slight increase normal? Will this harm the expansion tank since the bladder is set at 60 psi? I really want this to be a trouble and worry free system. Any advice is greatly appreciated.
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,350
    Location:
    Yakima WA
    I think you're fine. You didn't mention if you had set the pressure in the expansion tank to 60 psi to match the PRV, but your pressure is certainly well within safe range.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,647
    Location:
    Cave Creek, Arizona
    The expansion tank will selfadjust to the prevailing pressure. You cannot "eliminate" thermal expansion, but the expansion tank controls it, which is why there will ALWAYS be a pressure increase when the water heater operates, but not as great as if there were no expansion tank. The slight build up when you turn off a faucet could be "surge" caused by the water's inertia when the flow suddenly stops.
  4. DRG32

    DRG32 New Member

    Messages:
    5
    Location:
    Texas
    Thank you very much. I appreciate the help.
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