Noisy Pipes

[DSPGuy]

I purchased a house in October of 2024. I've noticed that when shutting off water faucets, I hear a sound sort of like pipes rocking. It's a sort of thump - thump within a half second of closing the faucet. It happens on both hot and cold sides of the faucet. When closing the faucets slowly, it doesn't happen. I thought that this is an obvious case of water hammer so I bought a pair of water hammer arrestors.

At the faucet which I had been noticing this most I added one of the arresters to the cold supply line under the sink. It had absolutely no effect on the sound. I thought that perhaps it was a defective device, so I replaced it with the other one. Still no difference. The majority of the plumbing is in the basement, so other than the risers to the sinks, bathtubs, and shower, it's easy to get to. It's all pretty solidly mounted. It is all solid copper.

I had my wife open and close the faucet upstairs while I was in the basement. I can hear it down there, but it seems to be coming from the entire house. It's impossible to get a bearing on which way it's coming from. Actually, I later discovered that it's happening with sinks at both ends of the house.

Any suggestions as to what might be causing this?

 

[PJB12]

Your system might have some vertical, dead-end pipes serving as water hammer arrestors, DSPGuy. They're common in inaccessible locations. (Instead of factory units)

If cold water only-
Turn off the water heater power and the outlet valve. (Or inlet valve if that is the only one.)
Try turning off the main and opening the lowest outlet in the house. Let the plumbing drain. (Opening the highest faucet will speed things along). Close the high faucet & the drain. Open the main very, very, very slowly and let the system fill. Bleed air from the faucets. This will restore the iar cushion in the dead-end pipe arrestors.

If hot water only or bot, do the same thing, but isolate the water heater so it doesn;t siphon, prolonging the emptying of the pipes.

The other (less likely) possibility is that a pipe strap in a wall broke. You will have to use a stethoscope or a stick to the ear and listen at various walls when someone else makes the bang happen.

Hope this Helps,
Paul

 

[DSPGuy]

Your system might have some vertical, dead-end pipes serving as water hammer arrestors, DSPGuy. They're common in inaccessible locations. (Instead of factory units)

If cold water only-
Turn off the water heater power and the outlet valve. (Or inlet valve if that is the only one.)
Try turning off the main and opening the lowest outlet in the house. Let the plumbing drain. (Opening the highest faucet will speed things along). Close the high faucet & the drain. Open the main very, very, very slowly and let the system fill. Bleed air from the faucets. This will restore the iar cushion in the dead-end pipe arrestors.

If hot water only or bot, do the same thing, but isolate the water heater so it doesn;t siphon, prolonging the emptying of the pipes.

The other (less likely) possibility is that a pipe strap in a wall broke. You will have to use a stethoscope or a stick to the ear and listen at various walls when someone else makes the bang happen.

Hope this Helps,
Paul

Paul,
Very informative. Thank you for that. I was completely unaware of the existence of water hammer arrestors built into the building's plumbing. However....

If my problem were due to the built-in arrestors no longer being functional, wouldn't my thump-thump problem have disappeared when I added the water hammer arrester to the sink's supply valve?

 

[PJB12]

I'm not sure I explained well. A screen shot is below.

If my problem were due to the built-in arrestors no longer being functional, wouldn't my thump-thump problem have disappeared when I added the water hammer arrester to the sink's supply valve?

To "refresh" the air cushion in each location, it's necessary to remove the water from that (those) pipes in order to create a new air space for the water to slam into. Installing a factory arrestor in one place doesn't necessarily drain the other chambers.

It seems that Job One is to determine which pipe(s) is banging. (Or wing it and drain the entire plumbing system absolutely completely.) When re-filling the system, fill very, very slowly. Very slowly.

And, keep in mind that the sound might not be from water hammer. Very common is from a loose or broken pipe strap in the wall. Lumber dries and straps come loose.

Is the noise from turning off only one, specific valve? If so, the valve might be closing too fast due to a loose washer jumping into place.
Solenoid valves are also notorious noise makers. (Washing machine fill, ice maker, dishwasher...) Do any of those machines cause the problem?

 

[DSPGuy]

Paul, I feel I understood your instructions on refreshing the built-in arrestors from your first post. Same understanding from your second post. That's not the question.

The question is, since adding my own arrestor to the faucet didn't fix it, is this really a problem of a built in arrester needing to be refreshed? Restated, since adding an arrestor had no noticeable change, is this a water arrestor problem at all?

To answer your other questions...
I've noticed the problem on my bathroom and kitchen sinks, as well as when the one of my toilets finishes filling. May be happening in other locations. I haven't thoroughly checked.

I've not ever noticed it on my washing machine filling, but again, I haven't really checked.

I do have a solenoid on the fill line to a whole house humidifier I installed. There doesn't seem to be any of this noise happening when it closes. But, I added an arrester to it at the same time I installed the humidifier because I pulled this humidifier from another house I used to own where water hammer with it was a problem prior to my adding an arrestor to its fill line.

 

[PJB12]

The question is, since adding my own arrestor to the faucet didn't fix it, is this really a problem of a built in arrester needing to be refreshed? Restated, since adding an arrestor had no noticeable change, is this a water arrestor problem at all?

I suppose if you put in an arrestor, it should not matter that the existing (if any) is not working on that particular faucet (only).. Is the new one the proper size?

You do have me confused. Is one faucet the problem, or more than one? If one, and it is the one with the arrestor, see above. if more than one, putting arrestors on one faucet won't help the others.

I've noticed the problem on my bathroom and kitchen sinks, as well as when the one of my toilets finishes filling. May be happening in other locations. I haven't thoroughly checked.

If many faucets/valves are causing the bang, perhaps a strap on the one pipe supplying all of them has come loose. Not being there in person this is just a guess of a very common cause.

Something I have not thought of is if your pressure is sky high. It should not matter unless it is really, really high- like far over 100 PSI-G. What's the pressure when checked? Super high pressure can cause pipes to jump hard if a strap is loose.

 

[DSPGuy]

I understand your confusion, as initially I was only noticing it on one sink. But later on, as this thread developed, I started noticing it on multiple faucets. So things went from singular to plural without me clearly explaining it.

I am starting to think that it is a loose pipe somewhere rather than water hammer. This is because lately I've started noticing some thumping, not only when turning the water off, but to a lesser degree when I turn it on. Correct me if I'm wrong, but I don't think that water hammer happens when water goes from off to on. Also, as I've been looking at this over the past 2-3 days, I am noticing it happening on more and more faucets.

The pressure at my house is only about 60 psi.

I'm not sure if the arresters I've been using are the right size. I searched in Amazon for sink valve water hammer arrester, and several of them came up, all pretty much the same size. So I would think it is. It's about 3-4 inches long, and about 3/4" in diameter.

I do think that the proper thing at this point is to continue to try to find any loose pipes. I have been doing that without finding any obvious problem pipes. But it's not that easy to try to track them down. I'm often by myself without someone else to turn the water off and on while I search for rattling pipes.

 

[PJB12]

Correct me if I'm wrong, but I don't think that water hammer happens when water goes from off to on.

That's correct. Water hammer is the slug of water slamming into a dead end.

The pressure at my house is only about 60 psi.

Sixty is peaceful.

I'm not sure if the arresters I've been using are the right size.

You could check at Oatey. Look on yours for the size. It will be marked from AA to F. Then check the chart at Oatey or another manufacturer. It'll guide you for sizing. As an example, I installed a Grohe GroTherm which shuts off instantly. I had to use a Size C, even though the supply is only 1/2" copper.

Unless that faucet is instant off, I suspect your device is proper for the valve.

I do think that the proper thing at this point is to continue to try to find any loose pipes.

Although it is a tedious job, I think you are almost at the next step at this point.

Before seeking a loose pipe...
I'd still figure out if the problem is hot, cold or both. Then I'd drain the entire pipe system absolutely completely (hot or cold or both) and fill very, very slowly. There may be a capped pipe arrestor that is water logged. (Bleed air at faucets also slowly.)


Should you determine that a strap is loose or broken, if you can get help, loosely holding the supply pipe to a faucet where it is accessible, such as in a basement, while someone turns the valve off quickly might reveal the culprit.

The hard part is to spot the bad guy pipe so you don't open walls needlessly.