Knocking/Tapping coming from PRV

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Gtribe5

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Had a plumber come out and replace a bad pressure reducing valve and install an expansion tank to the water heater. A few weeks later I started to hear a knocking/tapping sound coming from the area of the PRV.

I was able to get video of the sound coming from the area of the PRV, https://photos.app.goo.gl/8o3jvtpaQeBDtoLz7.

Had the plumber come out and he replaced the pressure reducing valve and right after he replaced it he heard the knocking sound. Plumber checked a few things around the house but he was stumped. I have no noticeable leaks in the house and when it does make that sound we are not using any water in the house (shower, laundry, dishes, etc). Is it another bad PRV or is the pressure set to high, plumber set it to 75psi.
 

Jeff H Young

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could it be sound transfer from elsewhere ? how high is the pressure coming in on street side of prv? I dont know if these are condos or your neighbors are a couple hundred feet away . if water isnt moving shouldnt be making noise, I doubt its a bad reg
 

Skoronesa

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Shut the main valve and see if the knocking stops immediately or slowly tapers off. If it does something in the house might be running a touch causing the prv to only open for a moment. I don't think the prv would make a sound like that though. It may be the pipe moving from thermal expansion/contraction. The piping will actually move a little when it heats/cools. Usually you get a sound where the pipe goes through a tight hole in a piece of wood.
 

PlumbNuts

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75 psi is the highest range for that PRV, it is also higher than needed for your home. Have your plumber adjust it to around 60psi and see if that stops the noise.
Taking a stab at it without actually being there: it is possible that the city pressure is much higher and with the PRV adjusted to it's highest range it allowing a form of water hammer to occur.
That is a very abnormal sound coming from the video and I am assuming that all of the noise that I was hearing was actually the PRV and not someone running lawn equipment next door.
 

Jeff H Young

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Plumb nuts touched on some points. 75 psi I never set them that high. I couldnt see video or hear it. If ir was my house or my customer I wouldnt be setting it at 75 and after having a problem at least twice Id lower pressure . so youve installed 2 reg recently? what about befor that was there no regulator? or is this actualy the third one youve had on house ?
prv can be noisy but never had a problem with 3 in a row
 

Dj2

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Another vote on 75 psi being too high.
You can reduce the PRV limit with the screw and double nuts below,
 

Gtribe5

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Thanks for all the replys. Still getting the noise after plumber set the PRV to 65PSI. I actually called the city water to check the meter which they replaced since they are doing this for all homes in my area he also checked the pressure from 2 fire hydrants close to my house which were 75 and 80PSI.

Should I try to lower the PRV some more? I do have an expansion tank on the water heater so I would have to match the pressure there also. Would I have to shut the water to the house before releasing air from the expansion tank?

Last time I talked to my plumber he said he would have to go into the crawl space to check the plumbing under the house.
 

Reach4

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Should I try to lower the PRV some more? I do have an expansion tank on the water heater so I would have to match the pressure there also. Would I have to shut the water to the house before releasing air from the expansion tank?
If the expansion tank is downstream of the stop valve for the WH water, you could just close that valve, and open a hot faucet.

I have never seen a city water PRV, and I don't know anybody who has one AFAIK. But while you are thinking about your PRV, some have filter screens. Since your PRV is new, probably not needed yet. I am not saying that sediment on your filter screen would cause noise.
 
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PlumbNuts

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Should I try to lower the PRV some more?
65 psi is an ok pressure (I typically set mine in our area at around 55) but yours is low enough to be safe on your plumbing system.
It also sounds like the city pressure is not too high in your area (75 and 80 at the hydrants) but those numbers could increase in non-peak usage hours.
I am at the point now of not thinking that the noise is pressure related.
 

Reach4

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For testing, you could lower the PRV to 30 psi without changing the thermal expansion tank precharge. Avoid taking a bath/shower or do laundry during the test, tho come to think of it, even those things would probably not cause a problem.

Remember when you are adjusting a PRV, you should dribble water somewhere.
 

Gtribe5

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If you were to turn off (unplug) your refrigerator, dishwasher and washing machine would you still here that noise with no other watr running?
Trying to rule out a solenoid issue....
The knocking sound is very random might hear it in the morning then again in the evening. I few times I've heard the noise and was able to turn a faucet on or flush the toilet and the noise goes away.
 

PlumbNuts

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The knocking sound is very random might hear it in the morning then again in the evening. I few times I've heard the noise and was able to turn a faucet on or flush the toilet and the noise goes away.
So it is random, not consistant; that is new info.
When it happens next, double check the appliances listed above to make sure it is not a solenoid valve causing the issue. Also check and see if you are getting the sound transfer that Jeff Young mentioned.
 

Gtribe5

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So it is random, not consistant; that is new info.
When it happens next, double check the appliances listed above to make sure it is not a solenoid valve causing the issue. Also check and see if you are getting the sound transfer that Jeff Young mentioned.
Sorry, I'm not familiar with the solenoid valve. Could I just unplug the washer, dishwasher and turn off the water going into the ice maker for the fridge (can see the wife being annoyed with the fridge off).
 

Reach4

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Sorry, I'm not familiar with the solenoid valve. Could I just unplug the washer, dishwasher and turn off the water going into the ice maker for the fridge (can see the wife being annoyed with the fridge off).
I think icemakers in refrigerators have a control to stop ice making. Some have a bail arm wire that gets lifted when the bin is full, but you can lift that wire manually, and it will stay up on its own.

The knocking sound is very random might hear it in the morning then again in the evening. I few times I've heard the noise and was able to turn a faucet on or flush the toilet and the noise goes away.
So you cannot relate it's start to any particular activity, and the duration is short enough that it going away when you do something that it could be coincidence, right?
 

Gtribe5

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I think icemakers in refrigerators have a control to stop ice making. Some have a bail arm wire that gets lifted when the bin is full, but you can lift that wire manually, and it will stay up on its own.

So you cannot relate it's start to any particular activity, and the duration is short enough that it going away when you do something that it could be coincidence, right?

Just unplugged the dishwasher and the clothes washer. For the ice maker there is an on/off switch which I set to off.

I noticed it a few weeks after the PRV valve was replaced. PRV was replaced cause the water heater was leaking from the relief valve, which fixed that problem. Sound happens randomly but when it does go off it may last up to 25 to 30 seconds. Today have not heard it but when it does happen we are not using any water in the house and usually turning on a faucet or flushing toilet makes the sound go away.
 

Reach4

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I noticed it a few weeks after the PRV valve was replaced. PRV was replaced cause the water heater was leaking from the relief valve, which fixed that problem.
It could be that your thermal expansion tank on the WH is not working. It should normally be empty of water. Knock on the tank to see if it sounds empty.
 

PlumbNuts

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Just unplugged the dishwasher and the clothes washer. For the ice maker there is an on/off switch which I set to off.
My intent was that when the sound comes back that is the time to turn off or unplug the appliances; Try one at a time until you can determine if it is in fact one of those or until you completely ruled them out.

I did not and do not expect you to keep your appliances turned off, my apologies for not having been more clear.
 
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