Get Rid of a Water Hammer

Learn how installing a water hammer arrestor will eliminate banging pipes. Find out what causes water hammer, and get tips on how heavy water rushing through loose pipes can cause pipes to bang around.

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LESLIE: Earl in Nebraska, you’ve got The Money Pit. How can we help you today?

EARL: Yes. You can help me by telling me how to solve a little problem I have with a knock on the washers behind my washers.

TOM: OK.

LESLIE: OK.

EARL: I installed, behind there, an air chamber or stub-out. And the washer is new and I didn’t want to have all that knocking, so I – when the valve comes on and I’m standing by the washer, it’s just – all I can hear is the valve.

TOM: Right.

EARL: But I went upstairs – it’s in the basement on a one-story house. I’m upstairs to a bathroom that’s above the washer and I hear a very loud knocking when I – still.

TOM: Mm-hmm. Well, that’s because you have what’s called “water hammer.”

EARL: Right.

TOM: And even though you installed that air chamber right near the washer, it’s probably not big enough to absorb the shock of the water as the valve opens and closes.

LESLIE: (overlapping voices) Absorb the sound?

EARL: OK.

TOM: Have you seen these – do you know what a water hammer arrestor is?

EARL: I do.

TOM: Mmm. That’s probably what you need. It has sort of a like a rubber shock absorber inside of it. Because water is really heavy; when you think about it, water weighs eight pounds per gallon, Earl. So with all that water and all the centrifugal force, when the valve opens and closes, you get that big bang. It’s because the pipes are loose and one other way to solve this is wherever you can access the pipes, to tighten them up with proper securing – with proper hardware to secure it to the wall studs. But typically, you can’t get to that.

But that’s what’s happening; the pipes are basically shaking, rattling and rolling and that’s what’s making the loud sound, because of the weight of all that water going through the pipe and then suddenly stopping as the valve closes. So the solution here is a water hammer arrestor, which is sort of a step up from what you did but that will make it a lot quieter.

EARL: I will give that a try.

TOM: Thanks so much for calling us at 1-888-MONEY-PIT.