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Plumbing - Dripping Between the Walls

Q. What are my options in finding (and fixing) a drip that I hear when I'm in one of our bathroonms? The sound is heard between the walls behind the sink. We have two bathrooms that "back-up" to each other (a symmetrical tub-to-tub, sink-to-sink and toilet-to-toilet effect). The strange thing about this is:

1) the house has to be completely quiet to hear the drip-drip-drip.
2) it is NOT audible when you are in the other bathroom.

I've checked the basement ceiling for "wet-looking flooring" but didn't see anything. This has been going on for at least three weeks, so I thought that the plywood floor would show water damage.

I'm afraid to ignore it. I should try and keep a diary of when it happens louder then usual and what water faucets were used (or not used). There are four of us living here, but I am the only male. Between my wife and two teenage daughters, the showers are running constantly.

Any suggestions would be greatly appreciated. You've helped me out in the past.

A. I suspect you have PVC waste pipes which make this noise and of little or no adverse consequence. Just Noisy.

Your likely PVC plastic waste pipes are behaving correctly, and noisily. They are tightly secured to the wall framing. When they expand from hot water (get longer) or contract and cool off (get shorter) they slide along the wood framing they are secured to. The temperature change from hot water draining through them causes a rapid expansion of the plastic pipe, and a plastic to wood framing "drip". This drip or bump noise or ticking sound occurs as the pipe gets longer with the warmer water flowing through it. When the hot water stops draining through the pipe, then the pipe gets shorter again as it returns to a neutral temperature and size.

When the house was built the plumber tightly secured these waste pipes, and they jump or rapidly slide against the wood framing ... which makes the sound. I call it an "earthquake" because it happens in an instant and not gradually. This instant move causes the bumping sounds which happens both when the warmer water begins to drain and again as the pipes cool off.

The solution is to cut open your drywall and loosen all the clamps inside the wall so the pipe slides smoothly along the wood framing, then close up the drywall, finish the drywall and paint. This is not usually worth the effort because the pipes are not causing any damage, only funny sounds.

Consider the wall noise as the personality of the house and live with it, or do open wall surgery to stop the noise. It is highly unlikely that damage will occur due to this occurrence.

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