Noisy Drain pipes - not water hammer?

Old 10-04-00, 10:15 AM
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I have a problem that my pipes bang when I drain hot water. I can fill the tub with hot water and I don't have any noise until I open the drain. Someone told me that it's a thermal expansion problem so I lowered the temperature of the Hot Water heater and that really didn't help. The noise is coming from a wall between two bathrooms. Could it be that the drain pipes are too close to the studs inside the wall or maybe a loose hanger? It seems that the dish washer causes the most banging followed by the shower. The house appears to have proper venting as there are two vent pipes above the baths and kitchen. Also, the noise doesn't seem to happen with cold water. Any help would be appreciated.
Old 10-04-00, 08:13 PM
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This is a weird one, normally thermal expansion or a loose pipe hanger wouldn't be a noise problem in a drain. I would have someone drain water while you listen and try to determine the location of the noise, hopefully it will be from somewhere that can be inspected without tearing up a wall, sometimes you can use a screwdriver for a stethascope to help pin point the location.put the handle to your ear and the blade against the wall and listen carefully,(you may want to put your finger in your other ear when your wife starts laughing) I would suspect a loose pipe banging against wood. If its going to be a major tear up, I would call a plumber, he may save you a lot of sheetrock repair.
Let us know what you find-plumber john

[This message has been edited by (edited October 04, 2000).]
Old 10-09-00, 05:54 AM
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Red face

I took your advice and tracked the noise to the drain pipe which rubs up against a floor joist in the cellar. Actually there is a shim between the drain pipe and the joist. I was able to look up inside the wall (w/o tearing up sheetrock) to find a cold water pipe very close to the drain pipe. I have no doubt that they were touching at one point so the previous home owner placed a shim between the floor joist and the drain pipe in order to move the drain away from the cold water pipe (maybe they were banging together at one point?). It seems that the shim has put a lot of torque on the pipes so any type of expansion makes the drain pipe settle against the shim and you get a LOUD banging noise (kind of like when a floor settles or squeaks but 100 times LOUDER!!). The shim is in there so tight that I was unable to move it with my hand - a hammer would definitely be necessary. Any advice where I should go from here? The noise is soooooo annoying that I have to fix this even if it means ripping up a wall, putting in a new section of drain pipe, etc.

Thanks for your help.....
Old 02-24-11, 12:58 PM
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Did You Ever Resolve This

I have the exact same problem. How did you fix this. Any ideas would be appreciated.
Old 02-24-11, 03:51 PM
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Welcome to the forums!! After 11 years, I doubt the posters are still alive on the forum. Describe your problem and what you see when doing a cursory inspection of your drain pipes. Moderators may move the post to it's own realm, but we'll find you.

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