Can a PRV be installed in line between street and house?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by larrymcg, Oct 18, 2010.

  1. larrymcg

    larrymcg New Member

    Messages:
    25
    Location:
    Silicon Valley
    The pressure in the house is 80psi and a PRV has been recommended. However, I'd like to reduce the pressure to the house and to the yard watering system. The line from the street comes up next to the house and splits. One line goes into the garage and the other goes into the yard watering system. Both lines have shut-off valves so I can independently turn the house and yard water on and off.

    Can a PRV be installed in the line from the street, under ground, before the line comes up out of the ground?

    --Larry
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,308
    Location:
    Yakima WA
    I see no reason why not, but I'd devise a way to have access to it and not just bury it. Given your location, I doubt if freezing is an issue. Do you know you will also need to install a thermal expansion tank before the supply line reaches the water heater?
  3. larrymcg

    larrymcg New Member

    Messages:
    25
    Location:
    Silicon Valley
    Thermal expansion tank? I guess I should find out what that is and why I would need one.

    Freezing? Sometimes water above ground will get some surface ice on it but it never seems to freeze all the way through. And any distance below ground doesn't freeze.

    --Larry
  4. Hardt

    Hardt Member

    Messages:
    44
    Location:
    Hawaii
    FWIW, I wouldn't bury in underground...it will corrode faster and possibly shorten its life and you wouldn't have easy access to it to adjust the pressure.
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,308
    Location:
    Yakima WA
    When a water heater heat water, the water expands and has to go somewhere. Before the PRV was installed, this expansion is easily absorbed by the city water main, so no problem. However, a PRV has a check valve that prevents this from occurring so the expansion has to find another place. The pressure rises in the water heater tank until it reaches the limit of the temperature/pressure safety valve on the tank and trips the valve open to release the excess pressure. This prevents the tank from exploding like a bomb. (literally) The thermal expansion tank provides a temporary space for this expansion to go. It is installed in the cold water supply to the water heater between the PRV and heater. It is charged with air to match the PRV setting. I understand that some newer PRVs have a bypass that allows for expansion, so you might check with your PRV for that feature.
  6. Hardt

    Hardt Member

    Messages:
    44
    Location:
    Hawaii
    Oh, I forgot to mention that I have a faucet before the PRV and its psi is 100+ and its great for spraying off moss, dirt, etc of the sidewalk, rock walls, etc. So I would think twice about reducing your 80 psi yard watering service!
  7. Terry

    Terry Administrator Staff Member

    Messages:
    14,794
    Location:
    Bothell, Washington
    Yes you can install a PRV below ground. It may be a good idea to box it though in order to have access to it later.
    Sometimes I replace old ones that have been buried. Kind of hard to find them that way.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,820
    Location:
    New England
    They make boxes for this sort of thing. You might use a covered one designed for sprinkler controls.
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