PRV placement relative to ball-valve

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DavidTu, Apr 16, 2012.

  1. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    Does it matter if pressure reducing valve is placed before or after the building supply main on/off ball valve?
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,247
    Location:
    Cave Creek, Arizona
    No, but it is easier to service and replace if it is after the valve.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,395
    Location:
    Yakima WA
    Seems to me the ball valve should shut everything off, so I put my valve where the supply line enters the house which is about 4 feet above the basement floor. The PRV is a couple of feet above that. This is one reason why I can't understand why someone would put their PRV at the meter.
  4. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    the valve should always be placed first.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,247
    Location:
    Cave Creek, Arizona
    When the PRV is at the meter it is to keep the high pressure out of the pipe to the house. SInce there is a valve at the meter, the PRV can be anywhere after the meter, regaridless of where the house valve is.
  6. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,395
    Location:
    Yakima WA
    HJ is of course correct, but if the supply line to the house is in such poor condition it can not withstand the high pressure, you will have a supply line problem in you very near future.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,247
    Location:
    Cave Creek, Arizona
    It does not have to be "poor", the main pressure could be so high, (which is why the PRV is needed), that it exceeds the recommendation for the plastic line used. Or someone may not trust the plastic to not fail at city pressure.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    While maybe not common, there are places where you need TWO PRVs, plumbed in series to drop the pressure to an acceptable level. So, if it was REALLY high, the utility might get it down to very high, then let you deal with it to drop it further, if needed. There's a limit on how much a prv can drop the pressure.
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