knocking drain pipe

Old 01-25-06, 12:44 PM
Thread Starter
Join Date: Jan 2006
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
knocking drain pipe

I have never run into this before just curious what the problem may be The 3 inch waste stack is knocking when the water is draining from the upstairs bathroom fixtures. It is not water hammer because it does not occur when the valves are closed, it occurs while the water is running through the 3 inch drain. THe pipe seems to move causing a knocking sound i have tried to anchor the pipe with straps vertically and horizion ally. Any ideas would be greatly appreciated?
Old 01-25-06, 02:38 PM
majakdragon's Avatar
Join Date: Jul 2003
Location: N.E. Arkansas
Posts: 7,475
Upvotes: 0
Received 1 Upvote on 1 Post
ifd112, Welcome to the DIY Forums.
If the drain lines are plastic, it could be that the water temps are causing it to expand and rub studs or joists. If you live in a cold area, the difference in temps of the ambient air and the temps of the draining water could cause this. It may be a coupling that is close to another surface that catches as the pipe expands or contracts. Good luck.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: