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Thread: PRV placement relative to ball-valve

  1. #1
    DIY Senior Member DavidTu's Avatar
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    Default PRV placement relative to ball-valve

    Does it matter if pressure reducing valve is placed before or after the building supply main on/off ball valve?

  2. #2
    Moderator & Master Plumber hj's Avatar
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    No, but it is easier to service and replace if it is after the valve.
    Licensed residential and commercial plumber

  3. #3
    In the Trades Gary Swart's Avatar
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    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. #4
    Plumber Winslow's Avatar
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    the valve should always be placed first.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

  6. #6
    In the Trades Gary Swart's Avatar
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    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. #7
    Moderator & Master Plumber hj's Avatar
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    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.
    Licensed residential and commercial plumber

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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