Clicking Noise While Sink Draining

[djberry55]

I recently purchased a new house and there is a clicking noise from behind the wall when either the sink is being drained or the bathtub is being drained. I tried a couple different non-invasive things that I found online, but didn't have any luck in fixing the problem so I went ahead and cut a 2ft x 2ft hole in the drywall behind the vanity to try to see what was going on and have the following observations:

1 - The noise occurs either when the sink is being drained or the bathtub is being drained; so it is not the supply lines. The drain for the sink goes into the wall, has a 90 degree elbow, and T's off into the main house drain about 18 inches away. The sink drain going through the wall does travel through a stud which I cut additional clearance around to make sure it was not hitting. Also, I noticed that this pipe was sloping upwards rather than downwards into the main drain line (not sure this is causing the noise, but thought I'd point it out).

2 - The drain for the bathtub also T's off into the main drain, but does so underneath the floor in the basement.

3 - The main drain line (which also appears to be the plumbing vent stack) is very close to the drywall on the other side of the wall and looks to be touching in some places. I did try placing some foam between the pipe and the drywall, but that seems to only make the problem worse. I was thinking that this contact was causing the problem, but being that I still hear the noise when the bathtub is being drained (which the water would come into the pipe below the drywall), I'm not so sure.

I was wondering if anyone had any advice on things to try.

 

[sparky472]

This is almost always caused by the vent stack not having enough clearance around it, and as water drains, the pipe rubs against the wood or drywall - particularly when it's hot water, which causes expansion of the pipe material. It's annoying, and my average-quality construction house suffers from it. There are some places where I've been able to get enough access to create additional clearance around the vent stack and solve the problem. And there are some places where I simply can't get to it. The foam, as you noted, just makes things worse - it only creates additional pressure between the stack and whatever it is rubbing against. The only way to resolve it is to create additional clearance.