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Old 04-16-2013, 08:44 AM   #1
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Can a defective Pressure Relief Valve do this?


I have 170psi through my municipal meter into a PRV into 1" copper, which keeps my house at 60psi.

BUT: When a single 3/4" fixture is open static pressure in the house falls to 40psi. Opening a second fixture anywhere drops it to 30psi.

Given the incoming sizes and pressures would you expect pressure to drop off this quickly and extremely? If not, can a defective PRV cause this behavior?

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Old 04-16-2013, 08:47 AM   #2
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Can a defective Pressure Relief Valve do this?


Yes it can.

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Old 04-16-2013, 09:04 AM   #3
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Can a defective Pressure Relief Valve do this?


Technically no, it can't, because when you open a faucet, the pressure isn't static anymore.


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Old 04-16-2013, 11:07 AM   #4
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Can a defective Pressure Relief Valve do this?


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Technically no, it can't, because when you open a faucet, the pressure isn't static anymore.
Meaning the PRV can't be responsible for the drops in static pressure I'm observing? (Note that the pressure gauge is on a pipe leg that is not in the line of flow.)
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Old 04-16-2013, 12:55 PM   #5
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Can a defective Pressure Relief Valve do this?


What Alan meant was perhaps you don't have your terminology right. Static pressure is when all fixtures are closed while working pressure is when one or more fixture is open. So I assume you are saying your static pressure is @ 60psi and your working pressure falls to 40 or 30psi depending on one or two fixtures being open. When the fixtures are closed again does your static pressure then return to 60psi?
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Old 04-16-2013, 03:06 PM   #6
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Can a defective Pressure Relief Valve do this?


Well the gauge I'm using is a Watts static pressure gauge, so the only numbers I can report are static. It makes sense that static pressure will fall when there is flow in the system.

Perhaps I should rephrase my question: Given my supply configuration is that level of drop in static pressure reasonable? If not, is it consistent with a problem in the PRV?

Or do I need to take flow rate measurements to determine whether I'm getting the maximum possible flow from my supply?
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Old 04-16-2013, 05:46 PM   #7
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Can a defective Pressure Relief Valve do this?


The more points of discharge the farther your pressure will drop. That is why waterlines are sized to provide the water you need.
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Old 04-16-2013, 06:59 PM   #8
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Can a defective Pressure Relief Valve do this?


water pressure vs water volume ??
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Old 04-16-2013, 08:15 PM   #9
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Can a defective Pressure Relief Valve do this?


Quote:
Originally Posted by joecaption View Post
Yes it can.

It most certainty can do that I have seen it happen many times and the only fix is to install a new prv


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Old 04-16-2013, 08:41 PM   #10
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Can a defective Pressure Relief Valve do this?


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Originally Posted by dbooksta View Post
I have 170psi through my municipal meter into a PRV into 1" copper, which keeps my house at 60psi.

BUT: When a single 3/4" fixture is open static pressure in the house falls to 40psi. Opening a second fixture anywhere drops it to 30psi.
Our city supplies @ 160psi, my PRV drops it to 70psi static, and we have all 1/2" CPVC. When our washer kicks on it drops to 50psi, and when I turn the utility sink on at the same time to drops to a varying 40-45psi. I realize our pipe size & type is different but our pressure drops are similar and my PRV is functioning properly. (I think?!)
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Old 04-16-2013, 09:22 PM   #11
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Can a defective Pressure Relief Valve do this?


It's a good practice to have a strainer before the PRV- some models have them built in. It's possible your screen may be dirty and affecting the flow
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Old 04-16-2013, 09:45 PM   #12
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Can a defective Pressure Relief Valve do this?


you may have a strainer before or in the prv clean and retry ...it may be a defective prv..ben sr
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Old 04-17-2013, 06:31 AM   #13
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Can a defective Pressure Relief Valve do this?


I would recommend you install a verified pressure gage before the PRV and a pressure gage after the PRV . Check the both pressures with everything off then have someone open a spigot or two while you stay and check the incoming and outgoing pressures, make adjustments while water is flowing and then leave it set there as long as the house side is not to high. If it don't adjust properly install a new PRV.

After checking strainer as advised.
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Last edited by COLDIRON; 04-17-2013 at 06:32 AM. Reason: aded text
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Old 04-17-2013, 10:18 AM   #14
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Can a defective Pressure Relief Valve do this?


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I would recommend you install a verified pressure gage before the PRV and a pressure gage after the PRV . Check the both pressures with everything off then have someone open a spigot or two while you stay and check the incoming and outgoing pressures, make adjustments while water is flowing and then leave it set there as long as the house side is not to high. If it don't adjust properly install a new PRV.
So what am I looking for? If static pressure after PRV is 60psi but with two taps running it drops to 40psi do I crank the PRV up so that under flow the static pressure reads 60psi -- even though with no flow it's probably going to be 75psi?
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Old 04-17-2013, 10:50 AM   #15
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Can a defective Pressure Relief Valve do this?


Did you check for strainers and if their clean ? If not post back for next question. Did you try it yet before asking the question? (gages in/out) Anytime there's a problem with something troubleshooting with results are required before moving to the next step.

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