We bought our home last November, immediately after moving in we heard a banging noise from the plumbing that appeared to originate in the area of the PRV. Noise sounds like something sliding then banging. It happens only with no water running and stops if a faucet is turned on. It happens sporadically throughout the day and night and will last anywhere from 5 seconds to 4 hours. It can be a singular event or come in a series. The system was pressurized to 65 PSI when we moved in, it is currently 50 PSI. One of the plumbers turned it back up to 65 days after the PRV was replaced and the noise became exponentially worse. The water usage is not above normal and the water meter does not move (it's digital) during the noise sessions so I don't think there's a water leak. There is no water purification or sprinkler system. After moving in we did find evidence of washing machine and refrigerator leaks as well as evidence of a leak from either the dishwasher or kitchen sink (none of which were found on the home inspection). Both the washing machine and refrigerator were replaced.

The house was built in '97. The previous owner lived here for 15 years. They claim to have never heard any type of noise. We've had 8 different plumbers to our home and are now thousands of dollars into this problem. After each attempted fix all water was drained from the system to 'remove any trapped air'. (Some of the work was for cosmetic reasons)

November - changed tank parts of all 3 toilets in the house
early December - changed the main shut off value (between the street and PRV)
mid December - drained water heater to remove any sediment buildup. Had City inspect the water meter.
late December - changed PRV (model LF 25AUB Z3)
January - changed valve stems in the shut off valves of all 3 toilets
late January - changed valve stems in shut off valves for all sinks in the house
Feb - Shut off water supply to all toilets, faucets, washing machine, dishwasher and water heater to isolate the source
Feb - new kitchen faucet. Replaced exterior hose spigot that had a damaged anti-siphon filter
March - installed expansion tank on water heater (Rheem water heater was installed 2017)
April - replaced 1 (of 2) shower fixtures to include the faucet cartridge

I'm out of ideas and very nearly out of money and patience. I welcome and very much appreciate any ideas or insights! Sorry if I missed any important piece of information and will gladly give it if you let me know what's needed.

It looks like someone is using the "shotgun" technique hoping something will cure the problem, but NOT finding the problem and fixing it first.

Yeah, it's been 6 months of trying to isolate and find the problem, which led to the discovery of other problems like shut off valves not working. Most of my actions have been guided by people in the plumbing profession.

Please teach me how to use a 'sniper rifle' so I can retire the 'shotgun'.

Every time you turn off the water at the valves outside your home and replace a valve, air gets into your system. Why a water hammer or air hammer happens can be tricky to locate the cause. Years ago the City of long Beach CA water systems in residences had air chambers (an 18" length of 1/2" galvanized pipe with a cap on top, installed above the outlet for each fixture water line. Over time these air chambers filled with water and rendered worthless. The industry responded with small devices called air hammer and water hammer arrestors which allowed the air inside the device to compress Which prevented the noise from a quick closing valve such as those on your Auto Dish Washer or Clothes washer. Often the cause can be pipes not secured properly which will pop and raddle inside the wall. Have you tried installing one of these devices? Can you access the pipes in the wall or attic to be sure they are all strapped securely? I do not know if one of these devices will solve your problem. The Arrestors are available from the sponsor of this site. Good luck and let us know if and or how you solve this problem.



Edited 1 times.

Thanks for the idea. I have not installed one. Where in the system would it be most useful? And would 1 be enough?

Water hammer occurs when the flow of water is suddenly stopped. If your noise occurs when no water is being used, it's not water hammer. Do you know what the water pressure is on the street side of the regulator? Has a gauge been installed, so the house pressure can be checked when the noise is occurring?

as steve said, if the noise occurs when nothing is running or shutting off then it is not water hammer. ( at least not in the sense that we normally call it)
on a positive note, it sure sounds like the plumbers made good faith efforts in trying to resolve this problem.
if the noise does occur when the digital water meter shows zero activity then I would take a hard look at the PRV.
other than that I don't have a clue ???

Actually "track down" the source of the problem and fix it. Just replacing parts, using guesswork, will eventually replace your system and MAYBE cure the problem.

That's the 2nd time you've said that hj, can you offer some ideas on HOW to track down the problem? The OP said he has had 8 licensed plumbers look at it so far attempting to "track down" the problem, and none have been successful.

The result only seems like a shotgun approach when you look back at 8 plumbers each trying to track down the problem in their own way. At any rate, it doesn't sound like he has much left to replace except the piping....

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Not a plumber by trade but a fierce DIYer

I do not know what, or how, the "eight plumbers" have attempted to locate the problem, but usually, if you can duplicate the symptoms you can trace them to the cause by careful testing.

Thanks for the responses.

Author: steve (CA)
Do you know what the water pressure is on the street side of the regulator? Has a gauge been installed, so the
house pressure can be checked when the noise is occurring?

I don’t see how I can get the pressure on the street side of the meter. Is that something I’d have to call the City for? I will get a gauge and post pressure when the banging is happening.

Author: packy (MA)
it sure sounds like the plumbers made good faith efforts in trying to resolve this problem.
If the noise does occur when the digital water meter shows zero activity then I would take a hard look at the
PRV. other than that I don't have a clue ???

I agree there’s been good faith efforts; problem is there’s been a lot of it! I’m hoping that it’s not the PRV, not the cheapest thing to replace.

Author: hj (AZ)
Actually "track down" the source of the problem and fix it. Just replacing parts, using guesswork, will
eventually replace your system and MAYBE cure the problem.

No kidding? I thought I was paying professionals for work and advice in an effort to avoid just doing random stuff. So HOW would YOU ‘actually track down the source’? Lead me to water. They're out of ideas. That's why I'm here. As always, snark is always appreciated and rarely helpful.

YOu are in Oregon, and I am in Arizona, so I CANNOT help the actual diagnosis, but To my memory, I have NEVER just started replacing things until I knew EXACTLY what needed replacement. There are MANY "plumbers" who lack diagnostic skills.

what is that saying? an infinite number of monkeys typing on an infinite number of typewriters will eventually write every book ever written.
great example (unless you are paying the monkeys)
on a serious note.
it does sound to me like the plumbers did some diagnosing and then relied on past experience.
I'm sure most of us (self included) have gone to a job and said "heck, I fixed one of these last week. all you need is a new__________" (fill in the blanks).
so I do believe that if everything that was done has not solved the problem , unless something defective was replaced with another defective part, the problem has to be with the PRV.
sorry I can't be of more assistance but if hj in AZ is too far to help, how can I help from here in MA.
good luck.

That PRV has a bypass feature for thermal expansion. When the pressure downstream of the valve gets to 10 psi above supply it opens. When the pressure was reduced to 50 psi, it gets there sooner. Add a potable water expansion tank to the system. That's just an educated guess. It fits your symptoms. Measure the pressure downstream of the valve and see if it creeps up.

paul, from the original post.


"March - installed expansion tank on water heater (Rheem water heater was installed 2017) ".

Thanks packy,
Quick question about the PRV: is there an optimum pressure range for these to be set to? The tag says 25-75. For example these may technically 'function' at __ psi, but not well or as intended.
The reason I ask is that the plumber who replaced the PRV in December came out yesterday and took a look at it. He turned up the pressure to 75, ran some water and turned it back down to 50. This was to try and jar free a spring-loaded something-or-other inside. The frequency and intensity has seemed to decrease, albeit it's been a short sample period.

I have another question. Steve asked about measuring the pressure. If there's really high or low pressure street side of the meter what could that mean? If the pressure swings noticeably inside the system during the noise what could that mean?

I missed that.....thanks. I'm sure they adjusted the pre-charge to the system pressure. What was that, 65 or 50?

reduce the pressure again to 45PSI. that is about the minimum you would want to go.
as for rating PRV's. the incoming pressure would dictate which one you used. incoming pressure of 95 might want a different PRV than incoming pressure of 185.

The expansion tank was charged to 50. If I bring the pressure down to 45, do I need to let pressure off the tank? Or is 5 psi difference ok?

do not confuse the hot water expansion tank with a well expansion tank.
one is much smaller and simply gives the expanding water a place to go. (hot water one)
one is much larger and allows the bladder pressure to aid in not depleting the whole house pressure so quickly thus preventing the well pump from cycling too often.

so even if your hot water expansion tank is set too low it will still function just fine.
obviously if it is set higher than your system pressure it will not do its job.

the short winded answer is to set the expansion tank pressure to 5-10 PSI below your system static (at rest) pressure.

I did not see this question going through the posts, but have you had the water supplier in to test their entry equipment? Of if you own it not the water company.

There may be a backflow preventer in the pressure regulator. If it is not working correctly, an adjacent user drawing high pressure water might be generating pulses in your feed. Maybe the converse as well.

Have you asked any adjacent owners if they are having any problems?