Water Hammer Causes House to Shake: How to Fix

LESLIE: We’ve got water pressure issues over at Bert’s house in Alabama. What can we do for you?

BERT: Hey, love you all’s show, by the way.

TOM: Thank you.

LESLIE: Thank you so much, Bert. So tell us what’s happening at the house?

BERT: The problem is that – and I tried to fix it. That’s why I’m calling you all because it didn’t work.

LESLIE: (chuckling) OK.

TOM: OK.

BERT: We have excessive water pressure and we know that. And I guess what I mean by that is between your water meter there’s supposed to be a regulator. It’s a diaphragm-type control valve you can screw down; control the pressure. Not one there. But not a problem because I’ve had – I mean even though the pressure is probably around 70 pounds per square inch, we don’t have any problems except this: my dishwasher, when it changes cycles, every time it shuts down a cycle it will shake the whole house.

TOM: Huh.

BERT: So I’m afraid something’s going to pop. So when we went to a large chain kind of place to get some plumbing supplies, they said to put what they call a water hammer in between your hot and your cold water lines for your washer and it would take care of that.

LESLIE: Well, a water hammer arrestor.

BERT: Yeah, that’s what it’s called; a water hammer arrestor. Thank you.

LESLIE: OK.

TOM: Right, mm-hmm.

BERT: And we did that and it did not fix the problem. Now, my house, I was told, was plumbed for two water heaters. So maybe is there a possibility that it’s just on a different kind of line and it’s maybe getting backflow?

TOM: Well this chatter that you’re hearing you’re saying is shaking the whole house. I’m thinking that you may have a bad valve on the dishwasher that’s doing this because very often if you have a bad valve it’ll make that chattering, shaking sound when the valve closes or opens. Is that what you’re hearing?

BERT: I don’t hear a chatter. I just hear the actual – I mean I was in – when I was in the military I did a lot of plumbing, stationary engineer work and it’s a back pressure. When the actual pressure cuts off, the back pressure goes through the existing valve structure. It does it to some degree or it did it to some degree on the washer but to none of the degree that should (inaudible).

TOM: Well, that is water hammer then and it might just be that you don’t have the water hammer arrestor in the right place.

BERT: Well, and when I asked this guy who was supposed to be a plumber that works at this large chain, he said put one on the inlet of both the – because I asked him. I said, “Well, how’s that going to fix my dishwasher?” and he said it’s all on one line. And that makes sense, you know, that it would just kind of (inaudible). Now, what I was told – and maybe you can help me with this – is that you can actually buy like a bladder and have a plumber install it somewhere in a main line that acts like an air cushion.

TOM: Well, absolutely. But that’s what a water hammer arrestor is. It’s like a pressure tank. And there are different types and some look sort of more like a pipe and others look like a tank; like a small tank that’s attached to it. What type of water hammer arrestor did you put on?

BERT: It was – I mean it’s brass. It fit on …

TOM: Was it about the size of a – did it look like a softball?

BERT: I’m in the medical profession. It kind of looks like an inhaler.

TOM: OK. I think that the kind of water hammer arrestor that you put on is not working for you. You need one that has sort of a diaphragm and an air tank and an air cushion. It sounds to me like you may have put it on but it’s not working for you. I don’t think you have the right type of water hammer arrestor. You may need a larger one and that’s probably going to stop this problem because this clearly sounds like water hammer. As the water runs through the pipes and the valve shuts off you have a lot of centrifugal force that shakes that pipe. Water’s very heavy. It weights eight pounds per gallon. And when you shut the pipes off very quickly with a valve, the pipes shake.

The other thing that you could do is make sure those pipes are securely attached if there’s an area where you can access them. Because if they are securely attached then there’s nothing to really shake.

LESLIE: Mm-hmm. If they’re fastened well to their surface.

TOM: That’s really the two things that you need to do, Bert. OK?

BERT: OK. Now let me ask you this. So this diaphragm; is that something I can install myself?

TOM: Sure, if you can do a basic plumbing project. It’s really not that difficult to do. It’s just a matter of cutting it into the pipe in the area close to the inlet valve.

BERT: Alright. Well that’s what I’ll try. I just – I was at my wit’s end and you guys have helped with other things that I’ve listened to.

TOM: No problem, Bert. Thanks so much for calling us at 888-MONEY-PIT.