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Thread: PRV and location for install

  1. #1
    DIY Junior Member acrod's Avatar
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    Default PRV and location for install

    My water pressure at the hose bib is at 85psi and from what I am told fluctuates quite wildy during different times of the day. My house is only 2 yrs old but I live outside the city limits and their is no requirement to have one installed, so the builders did not put one in. The water meter and shutoff are located underground. I know mostly everyone says to install a prv as close to the shutoff and meter as possible but it sounds like such a bear to install. How would I even be able to access the valve when repairs or adjustments are needed if it is underground? Can I install it closer to the house where it is not underground? The plumber I called is quoting me around $800 for install/materials of prv and water expansion tank, and I don't want to spend that kind of cash when I know I can do it myself.

  2. #2
    Plumbing Contractor for 49 years johnjh2o1's Avatar
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    Install it where the line first enters the basement.

    John

  3. #3
    DIY Junior Member acrod's Avatar
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    I don't have a basement and I have no idea where the line first enters the house. Is there a way I could find out where the main line enters?

  4. #4
    Plumber Cass's Avatar
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    Where is the main shutoff to your whole house...that is where you want to put it...

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default Prv

    At 85 psi, I would not install it, unless I knew for sure that the variations were extremely high.

  6. #6
    In the Trades Gary Swart's Avatar
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    The pipe from the street will come straight from the meter to the house. That's where the pipe will enter the house. There should be a valve right there to shut the whole house off. If not, I would seriously consider installing one. If you do install a PRV, you will need to also install a thermal expansion tank. That will got in the cold water line between the PRV and the water heater. The air pressure in the tank needs to match the pressure you set the PRV to.

  7. #7
    DIY Junior Member acrod's Avatar
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    the main shutoff is 20 feet away from the front of the house near the curb and water meter which is underground. digging is not something I want to do. I was told anything above 80 psi was too high for residential plumbing and can cause leaks and damage. I don't know if pressure had anything to do with it, but last year my prefilter on my water softener split in half. Oh if it helps any I have a manabloc system in my house.

  8. #8
    In the Trades Gary Swart's Avatar
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    I did not say you had to dig the pipe up. You know where the the main shut off is so think about it. If you were going to dig a trench to run a pipe to the house, would you dig a trench to a far corner or would you take the shortest way possible? Eyeball it. You pipe runs in a direct line to the house and there should be a shut off valve inside the house. A PRV would go in that line somewhere prior to any branch lines and before the water heater. A PRV has a check valve that creates a closed system which means water expansion due to heating can not be be absorbed by the city water main so the T/P valve releases to protect the water heater from explosion.

  9. #9
    Retired Defense Industry Engineer jadnashua's Avatar
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    Water pressure can, and usually does, vary throughout the day, so if it is nominally 85#, it could be well in excess of that in the middle of the night when most use has stopped. So, the first thing is spring about $10 for a screw-on pressure gauge with a tattle-tail (a second hand that records the max) and install it either on a hose bib, the water heater drain, or maybe the washing machine supply and leave it there for a day or so. Note the max.

    Where is the water heater located? The water often will come into the house near there, and you may be able to install the prv and expansion tank in that area (the expansion tank goes between the prv and the WH inlet on the cold side - see diagrams on the tank's website).

    Your house shutoff may only be outside...where I live, they put it inside, but we generally have basements and the water line is 4+ feet below ground level to keep it from freezing. Is there a shutoff somewhere in the house that shuts all of the water off? If so, you've found the location for the PRV.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  10. #10
    DIY Junior Member acrod's Avatar
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    from what I have seen it looks like everything comes in through the attic. There are no pipes outside anywhere coming in or out that I have access too. im still trying to find out where the main water line is because I can't see all the piping from the manabloc as it is covered over in attic insulation. This is frustrating.

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