Adjusting Water Pressure on a pressure reducing valve. PRV

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by LifeIsGood524, Mar 8, 2014.

  1. LifeIsGood524

    LifeIsGood524 New Member

    Messages:
    10
    Location:
    Apex, NC
    Hello folks, first post to this forum.

    I found a related thread from '07 - http://www.terrylove.com/forums/showthread.php?22151-What-is-Recommended-Water-Pressure .

    My house pressure as measured at an outside spigot is 100 psi. When I run the kitchen faucet, it dropped to 75 psi (100/75).
    I turned the PRV ~1 rotation CLOCKWISE and had the following readings: 100/80
    Another turn CLOCKWISE and had the following readings: 100/100 (this was as far as the PRV would turn in this direction)
    Recognized the trend and turned the PRV ~3 turns COUNTERCLOCKWISE and had the following readings: 100/70

    This is similar to what wraujr observed in the aforementioned thread.

    Question:
    why does the pressure return to 100 regardless of the PRV setting?
    preparing to install a simple irrigation system directly off the outside spigot. Should I go with the 100/70 setting?

    Thanks in advance for your insights,
    LifeIsGood524
  2. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,508
    Location:
    Houston, TX
    Once you adjust it you need to relieve pressure.

    If it creeps up, the valve may be bad, or your water heater could be increasing pressure, due to temperature expansion.


    Good Luck on your project. Welcome to Terry's Forum.
    Last edited: Mar 8, 2014
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
    New England
    If I'm understanding you, the outside stays constant, and the inside adjusts. If the outside stays at 100, it may be plumbed BEFORE the PRV, and no adjustment will affect it. This is commonly done, since it's nice to have max pressure on the hose.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,230
    Location:
    Cave Creek, Arizona
    You have a bad PRV. 100 psi is the incoming pressure. When you open a faucet, the PRV maintains whatever your set pressure is, but it cannot do it when there is no flow. Replace the PRV.
  5. themp

    themp Member

    Messages:
    77
    Location:
    NC
    I just had my water line replaced from the city meter to the house and the plumber had to put the PRV before the two lines that went to the house outside spigots that used to be before the PRV. He said it was against code now and sure enough the inspector said the same. I sure miss that 100psi for outside washing, etc. This is one code rule I do not really understand other than higher pressure more chance of failure. But this is copper to the spigots and has been that way for over 30 years.
  6. LifeIsGood524

    LifeIsGood524 New Member

    Messages:
    10
    Location:
    Apex, NC
    Thanks for the responses. Although I liked the thought that the outside spigots bypass the PRV, I don't think that is the case since the main shutoff (immediately below the PRV) also turns off the spigots. What I still cannot understand though is, if the PRV is bad and needs to be replaced, why then does it reduce the pressure when a faucet is running? With all faucets off, the guage reads 100 psi, regardless of the PRV adjustments. BUT, the PRV does impact the pressure when a faucet is open. By adjusting the PRV, I saw a reduction from 100 psi to 60 psi with one faucet open - it is clearly doing something. I just measured at the cold water inlet to the washing machine and saw the same results - 100 psi with no faucets open (not good) and 60 psi with kitchen faucet open.

    If the PRV is bad, how is it impacting the pressure when a faucet is open?

    LifeIsGood524
    Last edited: Mar 9, 2014
  7. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,508
    Location:
    Houston, TX
    Do you have a expansion tank on your water heater ?
  8. Reach4

    Reach4 Well-Known Member

    Messages:
    2,790
    Location:
    IL
    Imagine a perfect leak-free PRV. Now imagine that PRV shunted by a 1/16 inch inside diameter pipe. Your PRV is behaving like that; there is a small leak sneaking through.
  9. LifeIsGood524

    LifeIsGood524 New Member

    Messages:
    10
    Location:
    Apex, NC
    Yes, we do have an expansion tank. When adjusting the PRV, I see an immediate impact in pressure when running cold or hot water though.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    How long does it take for it to creep up from the set point after running some water then shutting the valve? It doesn't take much of a bypass leak for the pressure to rise, how big that leak is would determine how fast it rises...in comparison, that leak is insignificant while you are running water. Sounds like there's some small defect or debris caught on the seal.
  11. LifeIsGood524

    LifeIsGood524 New Member

    Messages:
    10
    Location:
    Apex, NC
    5-10 seconds to go from 60psi to 100 psi after shutting off faucet.

    Consensus seems to be a faulty PRV. It looks as though it can be taken apart. Has anyone had success in repairing a PRV? Are there recommendations on what to replace it with? Any gotchas in replacing? Attaching a picture that shows I do not have a lot of room to cut/replace existing assembly.

    LifeIsGood524

    IMG_1334[1].jpg
  12. Terry

    Terry Administrator Staff Member

    Messages:
    15,412
    Location:
    Bothell, Washington
    You may be able to locate the model from the tag, and then order the rebuild kit.

    Most plumbers just bring out a new PRV to make it a one trip job.
    Otherwise it can become two trips, office time to order the kit and waiting days for it to arrive. A simple service call winds up taking a week if you go the rebuild route.
    There are times it would be nice though.
    Last edited: Mar 9, 2014
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,313
    Location:
    New England
    Many companies sell rebuild kits for the theirs, but by the time you buy it, install it, it may be easier to replace the whole thing.
  14. LifeIsGood524

    LifeIsGood524 New Member

    Messages:
    10
    Location:
    Apex, NC
    There is a tag with the model. I'll try the rebuild route. Are there any gotchas to the rebuild? I see 6 screws on the face of the PRV. Assuming I can get to the innards there.

    On a separate but related note, I just returned from my neighbor's house where we found his pressure to be a hair over 40 psi. Odd thing is we could not find a PRV. We found the main shutoff in his closet but no PRV. We went to his crawl space and traced the incoming line to the pipe leading to his shutoff and did not find the PRV. The line coming back into the crawlspace from the shutoff lead to an expansion tank. He also has an expansion tank on his water heater in his garage.

    There must be a PRV, right?

    LifeIsGood524
  15. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,230
    Location:
    Cave Creek, Arizona
    I would never waste the time and money to "repair" a PRV, because in many cases, when you get done, it still malfunctions. Do NOT try to conceptualize what is happening, if it is not intuitive to you. Just take our experienced advice and change it.
  16. Reach4

    Reach4 Well-Known Member

    Messages:
    2,790
    Location:
    IL
    Unless he has a well, or his house is about 140 feet higher than yours.;)

    You may also need to replace your expansion tank. You could calculate how small of a trickle from a faucet lets the PRV work. If that trickle can be as low as 1 cup of water every 10 seconds, your tank is probably also shot. Replace or fix the valve first so you don't blow out the new tank.
  17. LifeIsGood524

    LifeIsGood524 New Member

    Messages:
    10
    Location:
    Apex, NC
    Just a tad condescending. This is a DIY forum. Those of us trying to do it ourselves typically want to understand what is going on. "Just take our experienced advice".....if you hadn't seen Terry's post, he just recommended ordering a rebuild kit.

    LifeIsGood524
  18. Terry

    Terry Administrator Staff Member

    Messages:
    15,412
    Location:
    Bothell, Washington
    hj is just telling like it is for us plumbers.
    For us, it's quicker and more apt to be good under warranty if we replace the whole dang thing.
    Plus, he's a grumpy old man. :)
    But we love him.

    I'm only in my 60's. That's makes me just a little less grumpy.
  19. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,230
    Location:
    Cave Creek, Arizona
    quote; Plus, he's a grumpy old man.

    Not really, but when we tell him that a any flow will cause the PRV to control the pressure, but any small leak will cause the pressure to reach the incoming level, AND they question HOW it con operate properly when water is flowing, that makes me "grumpy", because the alternate would be to give a dissertation on how the PRV works, and under what conditions is can work "sporadically". In other words, "just take out advice" the same as you would be a surgeon. If he tells you that you need a gall bladder removed do you argue with him and want to know why it has to be done?
  20. LifeIsGood524

    LifeIsGood524 New Member

    Messages:
    10
    Location:
    Apex, NC
    Replacing PRV

    If I go with replacing the PRV (vs repair), is the Watts 25AUB recommended? I also plan to replace the shutoff valve. Would an experienced plumber cut the pipe at the red arrows and replace the full assembly (pre-assembled)? Only have ~1" to work with pipes coming our of wall and both are CPVC (sigh) coated with paint. Should be able to clean them up and glue on new assembly of PRV and shutoff valve.

    Or is it possible to remove the PRV and shutoff individually? It looks like the second nut (second blue arrow) could be turned but the three others appear to be 'hardwired' into the assembly.

    Thanks in advance for your advice,
    LifeIsGood524

    P.S. Any advice on how to locate the PRV at my neighbors house? Really expected it to be at the main shutoff. Is it remotely possible the contractor placed it behind the drywall in the closet?

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