Noisy PRV - will arrestors help?

[Madumi]

I recently installed a new water mains & a PRV to bring the pressure from 85psi down to 55psi. After installing it, I noticed the sound while any faucet was on, like a dim reverberation, or a helicopter at a distance. The reverberation peaks & then stops once the faucet is shut off. I'm guessing it's the rubber releasing/equalizing pressure on and off till it balances.

Originally, the PRV was set to 45psi & the sound was worse. After setting it to 55psi, it's improved quite a bit, but it's still annoying (it can be heard from the kitchen & bathroom).

Is there any good way to dampen PRV reverberation? I'm considering installing arrestors on either side of the PRV, but don't know if arrestors are pre-pressurized (& if so, whether they won't dampen vibrations). Alternatively, I can jimmy rig some capsules on either side the PRV & fill them with something compressible & durable... dunno, just thinking aloud.

Any suggestions for reducing PRV vibrations?

 

[Jadnashua]

Did you also install an expansion tank? If not, do that and see what happens. Technically, when you add a PRV, you create a closed system, and then, when you use any hot water, reheating the tank causes the water there to expand, raising the pressure which you're trying to avoid. Without the PRV, it probably was just able to expand back into the supply system...now, the PRV prevents that.

Engineered water hammer arrestors are essentially a chamber with trapped air. SOme use a bladder, some use a piston. They might help, but you'll wear them out fast if you don't have an ET in the system, which is a big brother in function to the much smaller arrestors. Properly supporting the pipe and the PRV might help.

 

[Sponsor]

 

[Madumi]

Thanks jadnashua...

No expansion tank, but it's a Watts PRV with a relief valve (mains pressure is only 85psi).

Sadly I have no convenient place to put an expansion tank. I'd do it if that was the best fix, but I'd love to know if there's other options (?)

 

[Jadnashua]

Well, that means that every time your WH runs after you're done, your water pressure will rise to at least the supply pressure (probably a little more so it can open that valve). If so, it sort of defeats the purpose IMHO! Yes, it will rapidly drop back down again as soon as you open any valve, but in the meantime, you're putting pressure on all of the supply hoses (washing machine?, ice maker, faucets, toilets, etc.) and their seals.

FWIW, an ET can go anywhere in the cold line, but ideally should be between the WH and it's cold inlet shutoff valve. That's to ensure it can protect the system in case the valve gets shut off, otherwise, everything from the WH forward will see upwards of 150psi until the T&P valve on the WH opens to relieve that pressure. The pressure can easily and quickly get that high in a closed system very quickly because copper pipes do not stretch much! Your hoses will balloon a bit, though.

Hammer noises occur when water gets shut off quickly...inertia causes the pipe to try to keep moving. An arrestor works best when at the point where that valve is closing. If it's the operation of the PRV (might be defective), IF an arrestor is likely to work, it would work best on the inlet to the thing as the supply pressure gets stopped...the arrestor gives it a place to go and cushions the impact, hopefully enough to damp the noise and absorb the impact.

 

[Madumi]

Thanks again...

Just to be clear, the noises are not hammer noises from shutoff valves. It's a persistent low hum while any faucet is on.

Given that it's coming from internals of the PRV, would I need something to damp the noise behind it as well as in front of it (the supply line also goes a fair distance through the house).

Is there anything else beside an expansion tank that could do the trick? thx!

 

[hj]

are you sure you did not install the PRV backwards, because that is the usual reason for that type of noise.

 

[Madumi]

I'm almost 100% sure I didn't install it backwards, but I'll double check.

If it helps, here's an audio clip of the hum (opening & closing a faucet). Audio has been amplified so it's clear:
https://soundcloud.com/medoomi/prv-hum

thx!

 

[Jadnashua]

If a valve is vibrating at a high enough rate, it could sound like a hum. Typical water hammer only occurs when you shut off a valve - the inertia of the water then slams into that now closed valve, often moving the pipe, creating the impact noise.

 

[Madumi]

I just checked the PRV & it's installed correctly (arrow aligned with water flow).

I'm guessing that an expansion tank might help some. Is that that the best option?

Another concern is that the sound resonates along the supply line backwards (through the house), as well as forwards. I'd prefer not to have to install two expansion tanks (on both sides) just to deal with this sound. Surely there's an easier way?

 

[Sylvan]

"(mains pressure is only 85psi)."

Why do you need so much pressure?

Excessive pressure can cause erosion on ferrous and non ferrous metal piping, causes hydraulic shock when a quick closing valve such as a solenoid closes

Even a flushometer normally requires less then 30 PSI to operate properly

Say you have 60 PSI it will elevate water to a height of 138.6 feet then you take friction loss int consideration you still will have more then enough pressure for almost every residential application

Sometimes more is bad for a plumbing system

 

[Jadnashua]

There is no technical reason to add an ET prior to the PRV. What may be happening, and this is certainly just a guess, is that without an ET, after using any hot water, while the water heater is running to restore temperature, the water is expanding, and the resulting pressure is pushing its way back through the relief valve in the PRV (note to others, not all PRVs have a relief valve, but apparently, this one does). Stopping that expansion may stop it. From a functional standpoint, a PRV and an ET go together like peanut butter and jelly...it works best with both. It could simply be a malfunctioning PRV, and a new one, or maybe a different brand might solve it. Without an ET, at times when your WH is running after you stop using water, the pressure in the house will rise at least to the level of your supply (if it has a relief valve), or it can rise to the point where the safety valve on the WH opens (the T&P valve). Sometimes, there's a leak in the house that limits the pressure rise ( a leaking faucet, or some toilet refill valves will leak). FWIW, most PRVs don't make any sounds until they're failing or are defective.

 

[Terry]

If it helps, here's an audio clip of the hum

thx!

You forgot the Seagulls in the recording.

 

[SteveW]

Hard for me to see how lack of an expansion tank could cause a hum while water is running.

I would think that there is a loose gasket or something like that somewhere in the path of the flowing water.

I'd be tempted to take the PRV out, check to make sure no obstructions, (make sure it really is in the proper direction per HJ), and reinstall.

 

[Master Plumber Mark]

I threw a Wilkins prv valve into a house last week and it was defective from the get go...
it literally chattered and hummed and the guages bounced up and down like a yo-yo...

I was lucky that I had another Watts valve buried in the bowels of my truck...
I cleaned all the dirt off of it and installed the valve in the place of the original new one..
It cured the problem and I saved killing the whole day fooling with this problem..
Took the new wilkins back to the supply house and got a credit for it.....


You probably have a bad prv valve... sorry you have to change it out.....

 

[Madumi]

Thanks again for replies...

@Sylvan, PRV was on 45psi, but it made more noise, so I increased it to 55psi (makes less noise), street pressure is 85psi

@jadnashua, the noise persists before there's any measurable increase in pressure in the system. I'm pretty sure it's not the hot water heater. the relief valve on the PRV would only engage after the system goes higher than 85psi (street pressure).

@Terry, sorry, forgot the fries

@SteveW, I might try that... There's been no additional fittings/loose faucets attached. The vibration clearly comes from the PRV (heaviest vibrations begin there).

@Master Plumber Mark, Hmmm, if I had a spare one, I'd certainly try to change it out.

One detail I forgot to mention, didn't think it was that relevant, was that I cheaped out. Fitting at the water meter is 3/4", line from the road to the house is 1", but the PRV I put in is a Watts 3/4"... Would a 1" make less noise, or more?

 

[Cwhyu2]

What is the number on PRV tag, I install Watts 25AUB PRV. The reduction in size should not really cause the sound you are hearing.
I`m leaning towards a faulty PRV.

 

[Reach4]

I would try turning up the PRV to 75 or 80 to see if that works around the problem. That would be a method that would be within the rules I think. A downside of higher pressures in the house is that water hammer could become a problem.

An expansion tank might damp the oscillation out, but that is another big piece that could fail in the future. Would a water hammer arrestor do the job? I don't know. They have a piston which would have some mass. So would that make the arrestor not as good as a thermal expansion tank? If you tried the experiment, then you would let us know. Would it be more effective on the input or output of the PRV? I don't know that either.

If I were confident that the mains would stay under 90, I would consider getting rid of the PRV if it were my house. I am not a pro, and I am not suggesting that what I might consider is right. If you have water towers in your area, the peak pressure would tend to be in the wee hours of the morning as the water is pumped higher while the electric rates are low and demand is low.

https://terrylove.com/forums/index.php?threads/prv-causing-pressure-mayhem-chatter-hammer-during-flow.66251/ is a case with a very different (slower) oscillation, but you might find it interesting anyway. The cure was choosing a different PRV.

 

[Madumi]

Well, that was a little underwhelming... I decided to up the house pressure from 55psi to 65psi & just see. The noise ceased at 60psi, so that's where I've set it.

The unit is a Watts LF N55B M1 (discontinued), so I'm guessing it's only good for reducing incoming pressure by 25psi. Noise begins when it's asked to reduce more pressure. Seems a little deficient, but Oh well, problem solved

Thanks so much for suggestions. Glad I didn't have to go the arrestor/expansion tank route!

 

[Reach4]

I am glad to hear the oscillation stopped.

LFN55B-M1 is not discontinued
http://www.watts.com/pages/_products_details.asp?pid=6809

N55B-M1 (no LF) is discontinued.
http://www.watts.com/pages/_products_details.asp?pid=3431

 

[Jadnashua]

IF you want your home's water pressure to actually stay at the PRV setting and not rise each time the WH reheats water, you can live without an ET. But, if you DO want it to stay constant, you still need an ET in your system.

One thing to understand is that the utility's water pressure is not likely constant through-out a 24-hour period. It can rise significantly when there's not much use or they are trying to refill a water tower (often late at night or really early mornings). Plus, as things get built, they may add a pumping station, or even just boost things to ensure those at the end of the line get decent water pressure. If the pressure does go up, that relief valve in the PRV means your house water pressure will just rise again to at least the supply pressure (which now could be much higher). That rise/fall in pressure isn't great on things like flex lines to toilets, sinks, washing machines, etc. PRV+ET go together.