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bajaboy1 11-21-2007 08:57 AM

Noise expert needed
Ranch house, full basement. This only starts when it's cold out. Turn on the water in the bedroom, mostly warm to hot water, and the drain vent starts banging, knocking. I guess it's expansion, but not sure how to stop it. I have access in the attic to it but not sure what to do.


Mike Swearingen 11-21-2007 10:58 AM

I'm no "expert" on anything, just a long-time DIYer.
If the vent pipe is loose, maybe you can clamp it down better where you can reach it, or tap wedges in around the pipe in the holes where it passes through wood framing to help alleviate the noise.
Plastic drain/waste/vent pipes are just naturally noisier than metal pipe. Sometimes you can wrap insulation around them or spray foam around them to help quieten them down.
Good Luck!

bajaboy1 11-21-2007 11:19 AM


Thanks for responding. I'll check the clearances around the holes.

That one Guy 11-25-2007 11:15 PM

That doesnt make sense? Are you sure its the vent or is this some type of water hammer? I dont know why the drain vent would make noise when the water is turned on.

bajaboy1 11-26-2007 09:00 AM

Thanks for responding.
Well, I'll try to detail a little more. When warm or hot water is turned on in the master bath, a banging occurs behind the wall and up through the ceiling into the attic. This continues for a couple minutes after the water is turned off and done draining. No other water is being drained at this time, the water drain drops about 10 feet from there, along the basement wall and into the basement concrete and off to drain. The basement is well insulated, including that wall. This occured before I finished the basement anyway. This starts happening this time of year, when it gets cold out.

bajaboy1 11-28-2007 07:22 AM

Any other suggestions? Vent piping seems to be tight through the attic. Got to be the venting pipe. I can hear it while the water drains while up in the attic. House is only 5 years old, if that matters.

That one Guy 11-28-2007 03:35 PM

Do you have any pumps? water or sewage?

bajaboy1 11-29-2007 06:33 AM

No pumps.

Can it just be the cold air coming down the vent from the roof and the warm water hits it as it's draining? I guess if water is flowing down the drain, wouldn't that create a small vacume pulling air down the vent?
Just thinking out loud here.

Ron The Plumber 11-29-2007 10:03 AM

What type of pipe is the vent? ABS, PVC?

bajaboy1 11-29-2007 12:07 PM

It's PVC.

Ron The Plumber 11-29-2007 12:13 PM

Now when hot water runs through plastic drain pipes, it can cause them to expand. This could be the cause.

bajaboy1 11-30-2007 08:26 AM

Any solutions? Only happens when it's getting cold out. Would it help any to insulate the vent in the attic? That's the only place cold air hits the outside of it. Cold air coming down the pipe, I'm not sure what could be done there.

Ron The Plumber 11-30-2007 08:40 AM

No solution without accessing all related pipes.

bajaboy1 12-05-2007 09:29 AM

What should I look for on all related pipes?

Ron The Plumber 12-05-2007 09:41 AM

Pipes too tight to the studs or floor joist.

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