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I have a mixer tap in the kitchen that has been causing an increasing amount of water hammer sounds in the pipes in my utility closet and behind my wall. There is almost no way to shut off the tap without causing the sound, even if done softly.

A plumber who just visited insisted that the problem is with the tap itself, whose valves appear worn out, and replacing the tap would solve the water hammer issue.

To demonstrate his point he had me notice how no other tap in the house causes the water hammer sound even if shut off violently.

When I mentioned that I heard others suggest that installing a water hammer arrestor on the affected pipes is a potential solution, he said that he considers it an expensive solution that's not worth the effort, and that the tap would remain an active issue.

Before engaging in an unnecessary tap replacement, I wonder if his assessment checks out—will replacing the tap actually solve the issue as he says, or will it prove a temporary or incomplete solution?

EDIT: The same plumber just came here again and we found a complication. Changing to a different tap didn't stop the water hammer.

He had a look in the crawlspace beneath the house and was able to identify the pipes that are shaking, and will now fix them in place with some expanding foam.

But I'm worried that fixing the noise won't reduce the risk to the pipes themselves. Can my pipes still silently fail due to the pressure? Replacing the faucet didn't seem to stop the water hammer issue, so will the pipes keep deteriorating even once we've fixed the sound?

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  • compare the labor and tap cost compared to the labor and arrestor cost plus the new tap because it will fail anyway... Sounds to me like you have a good plumber...
    – Solar Mike
    May 25 at 12:18
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My answer is based on this:

I have a mixer tap in the kitchen that has been causing an INCREASING amount of water hammer

It sounds like the plumber properly diagnosed the issue and can see that the valve is worn out. The more you use it then the more worn out it gets thus explaining the increasing amount of water hammer.

If the issue can be solved without a water hammer arrestor then I would go for that solution. Consider the pros of not installing an arrestor:

  • One or more fewer points of failure
    • The tap is required, an arrestor is an accessory
  • Arrestors can fail for various reasons and the hammer will return

If you install an arrestor then you're only hiding the problem.

Yes, the arrestor will absorb the noise but all that water force is still being exerted in your pipes. If you're only taking care of the symptom then the water hammer can still cause joints to fail and then you'll have a much bigger problem on your hands.

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  • Makes sense. The same plumber just came here again and we found a complication. Changing to a different tap didn't stop the water hammer. He had a look in the crawlspace beneath the house and was able to identify the pipes that are shaking, and will now fix them in place with some expanding foam. But your comment regarding the arrestor only absorbing the noise still worries me. If the plumber manages to stop the water hammer sound, are my pipes still at risk of silent failure due to the pressure? Is this a concern I should raise with the plumber? May 25 at 13:15
  • @GabrieleCirulli So slowly closing the new tap still causes the hammer?
    – MonkeyZeus
    May 25 at 13:25
  • @GabrieleCirulli You should check if your house is equipped with a pressure reducing valve. If it's not working properly then it could be introducing excessive pressure in your house's plumbing.
    – MonkeyZeus
    May 25 at 13:28
  • the plumber has just finished wrapping the pipes with insulating foam in an attempt to reduce vibration. I will be able to test for sounds in about two hours. But yes, even before the intervention, closing both the existing and new tap still caused the pipes to shake. I looked at the water mains and don't see something that looks like a pressure reducing valve. If it's any indication, the water pressure I usually get from my faucet is on the average side, not high at all. But I'm not sure how else I could assess the amount of pressure within the pipes. May 25 at 15:00
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I would have said your plumber has absolutely no knowledge!

Water hammer is caused by loose pipes and can always be fixed by eliminating the pipe movement.

Once the pipes are fixed in place there will never be an issue, and the faucet was not the problem. The loose pipes were.

Arrestors are not that expensive but they don’t always work again anchoring the pipes always works.

If he anchors them with foam and eliminates the movement there is nothing to worry about.

If the foam is not enough of an anchor strap them and forget about it.

I just checked the orange big box store has 3/4” in line arrestors versions for 12.86$ how is this expensive?

The problem gets worse with time as the pipe slamming back and forth chews up the framework. Allowing the pipe to move more and more so even a subtle change in flow can cause hammering.

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