Water Pressure Too High

Discussion in 'Plumbing Code Questions' started by Ismplumb, Mar 22, 2020.

  1. Ismplumb

    Ismplumb New Member

    Joined:
    Mar 22, 2020
    Location:
    Georgia
    Home inspection shows that water pressure in the house is too high.

    I verified the pressure to be 120 PSI at the inlet to my washing machine. I tried to regulate the pressure at the Water Pressure Reducing Valve but the pressure didn't change.
    However I noticed that when I open a faucet in the house the pressure drops to 50 psi. Also, I notice that the pressure is adjustable when a faucet is open.

    Is this normal or is there an issue? Am I testing the pressure wrong?

    Thank you.
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    OK, what you described is normal to a point. But then when you turn off that faucet, and the water heater does not turn on, the pressure should not rise back up. If the pressure rises back up, the PRV is bad. It may be rebuildable with a rebuild kit.

    With a PRV, and today often without a PRV, you should have a thermal expansion tank. The symptom of not having a working expansion tank is that the pressure rises a lot after using hot water, you stop using water, and the WH heats. The thermal expansion tank should absorb water, and limit the rise due to thermal expansion.
     
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  4. Ismplumb

    Ismplumb New Member

    Joined:
    Mar 22, 2020
    Location:
    Georgia
    Ok. thanks i will look into it.

    The challenge now is that the body of PRV and pipe is behind a sheetrock and in a tight corner next to my water heater (I will have to decide if I want to try doing this).

    BTW, could this high pressure be a reason for a thudding in the wall when bathroom faucet is open and also sweating toilet pipes and tanks?
     
  5. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Maybe on thudding. I don't know. For sweating, the mechanism would be that the high pressure causes the fill valve to leak water almost continuously. That would make for a continuous flow of cold water. Lift the tank lid, and expect the water to be up to the top of the overflow tube, rather than a typical 1/2 inch below.
     
    MASTERPLUMB777 likes this.
  6. Terry

    Terry Administrator Staff Member

    Joined:
    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    PRV valves don't work correctly forever. At some point they need rebuilding or replacement. Most plumbers plan on replacement as parts mean a second trip out and may not even be available.

    Too high a pressure is hard on everything in the house. Code only allows up to 80 PSI.
    If a toilet tank is sweating, like mentioned above, it may need parts in the tank, like a new flapper or fill valve. Sometimes an adjustment.
     
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  7. Ismplumb

    Ismplumb New Member

    Joined:
    Mar 22, 2020
    Location:
    Georgia
    The thudding sound is startimg to piss me off. I know I have a high pressure issue = bad PRV.

    However before going into the wall I want to eliminate other possible causes of the thudding sound. This sound is heard only when hot water is running from one bathroom.
    No sound is heard when water runs from the master bedroom bathroom and the half bathroom in the house.

    Could I try something else to resolve the sound?

    BTW, sweating toilet tank and pipes were fixed. The toilet tank to bowl gasket was bad. I replaced it but it didn't fit right so I changed the whole toilet tank kit.
     
    MASTERPLUMB777 likes this.
  8. Jeff H Young

    Jeff H Young Active Member

    Joined:
    Feb 27, 2020
    Location:
    92346
    Just went through this on my houseI Installed new prv 3 years ago it was "creeping up in pressure" run water drops to set pressure then after awhile it raises back up.. So mine being relatively new I rebuilt it but it was almost as much as a new one. @ of my toilets were causing water hammer even after the prv repair. So I put new fill valve on toilets that dont slam shut I have fluidmaster and you can repair those or simply replace.
    Id say replace prv befor trying to solve hammer
     
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    The higher the pressure, the more energy there is when you shut off a valve. That increased energy can force the pipe to move through inertia...think about hitting something with your car, the faster you go, the more likely you'll have issues...same idea with water pressure when you try to stop the flow - water travels through the pipes when the pressure is higher.

    Some things are more prone to creating water hammer: the icemaker in your frig, your washing machine, and some toilet fill valves. There are a few other things, but those are the most common. Keeping the pressure down may just solve your problem.

    If you have an expansion tank, it may be shot. IF the pressure creeps up slowly, the PRV may be shot.
     
  10. Jeff H Young

    Jeff H Young Active Member

    Joined:
    Feb 27, 2020
    Location:
    92346
    Change prv first then see if you have a hammer
     
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