I know that the pressure from the street is over 90psi in my area.

I have a pressure regulator (about 5 years old) on my main line and when all faucets are off and not drawing water the psi is set and maintains at 80psi. Plus I have an expansion tank on my main water heater and it is roughly 5 yrs old.

However, I notice that I have had very inconsistent water pressure at various times of the day. For example, today at 230p I saw 80psi on the meter then turned on an upstairs faucet and saw the meter drop to about 45psi with it open on full (and not coming out with a strong flow). Once I closed the faucet it returned to 80psi.

Similar experiment just now... started at 80PSI, turned on downstairs faucet1 right past the reduction valve and only dropped to 75, turned on the next faucet downstairs and dropped to 55psi.

I brought a plumber in who installed the reduction valve and he said that it was fine and this was a mystery.

I thought that setting the valve to 80PSI meant that it would maintain 80PSI under usage as long as the street was coming in higher than 80.

Does anyone have any ideas as to what the problem could be here? Does this sound like the reduction valve is going bad? Any suggestions would be greatly appreciated!

  • Where are you reading the water pressure? You say "meter," but I don't know if you mean the utility meter or a hose bib pressure gauge (meter). Where you read your pressure is important. Also, how old is the plumbing? Is it copper, PEX, galvanized, etc.? You should expect a 1psi drop for every 2 feet of elevation gained, and some head loss depending on flow rate and flow resistance, but more information on pipe material, nominal diameter, length, and age would help greatly.
    – Hari
    Feb 6, 2017 at 20:56
  • Also your describing both pressure and flow. Be careful as flow increases pressure decreases. Pressure is highest at no flow.
    – Tyson
    Feb 7, 2017 at 0:50
  • Great feedback. Pressure is from inline pressure gauge installed right after the pressure valve. Pipe is mostly copper feed with some quarter and half inch but mostly quarter. Age of plumbing ranges from 20-30 yrs to 10 yrs
    – Ron Iller
    Feb 7, 2017 at 21:37
  • as for the pressure and flow comment, I get you. The sad thing is that with the 15psi drop I described, the flow was weak so not exactly sure where that 15 went... I probably have an extended plumber's visit in my future to hash this out
    – Ron Iller
    Feb 7, 2017 at 21:56

1 Answer 1


If this is the gauge on the PRV output, you have a restriction on the intake side of the PRV or in the PRV itself. I suppose it may also be possible that your plumber installed a valve that's too small for your connected devices' flow rates.

As an aside, you also have a dimwit for a plumber if that's "a mystery" - or your plumber is lying to you, which comes somewhat lower than dimwit in my book.

You (or your new, hopefully competent and truthful plumber) will need to remove the PRV and see if there's something like an intake filter screen that is clogged with debris, pipe scale, etc. restricting flow into the valve, and if not, go looking for something stuck in the inner workings of the valve itself. You may wish to add a more easily serviced filter suited to the full street pressure on that intake side, as well.

  • I agree, + with 90 psi at the source or even 80 the 5 year old regulator is not working correctly since it was in the past. hopefully the "plumber " installed a shutoff before the regulator so it can be serviced or replaced.
    – Ed Beal
    Feb 7, 2017 at 2:56
  • Thanks. There is a shutoff in front of it. Looks like I need to go hunting for a good plumber
    – Ron Iller
    Feb 7, 2017 at 21:41
  • Can you post a picture of the PRV? Some have a rather obvious built-in filter that should be easy enough to clean since you have a shutoff. The one in an answer here, for instance, appears to have an "obvious" filter screen access: diy.stackexchange.com/questions/108196/…
    – Ecnerwal
    Feb 8, 2017 at 15:43

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