thunking sound in pipes

Old 12-15-06, 10:43 AM
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thunking sound in pipes

(I'm revisiting a post of mine from a year ago. I forgot about the problem for a few months because it subsided, but now it's back.)

When we use fixtures on the upper floor of our home, there's a rapid thunking or thumping noise as the water runs up the pipes. It sounds like it's coming from a vertical pipe that is behind the walls. Then, when the toilet stops filling, for example, there's a mild bang--a classic case of water hammer, I suppose.

I tried to find the "knock stopper" product suggested in a reply to my last post, but the only thing I came up with seemed to be specifically for washing machines, and that doesn't appear to be my problem. Maybe I need to go to a plumbing supply store for a larger selection.

Meanwhile, I've tried the procedure where you shut the water main and then open the highest and lowest faucets in the house to allow air into the system, but that doesn't appear to do much. Maybe I'm not doing it quite right--for example, the advice I've seen says to wait until the water is completely drained from the lowest faucet before closing it and turning back on the water. But it seems to take forever until the last trickle of water emerges from that lowest faucet. Are you supposed to wait for those last drops, or just until the flow has slowed to a tricke? Does it matter? Any fine points to this procedure that might yield better results?

Might this problem be solved with water hammer arresters? If so, does it require professional expertise to know exactly where and how to install them? It looks like I may need a plumber, but I at least want to first see if there's anything simple I'm overlooking.

Thanks for any advice on this.
Old 12-29-06, 09:11 AM
Join Date: May 2006
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Not sure if you've resolved your problem with water hammer but here's my experience.

I had a similar problem throughout the house. I purchased a pair of water hammer arresters from HD but realized they were meant to be installed near the source of the hammer. In my case it was in almost every fixture so it wasn't practical.

I had the pressure tested and turns out the water main was pushing 85psi into my plumbing system whereas normal should have been 45-50. I installed a regulator on the main line and it eliminated the problem throughout the house.

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