Simulated dripping coming from black ABS?

Is it possible for black ABS drain pipe to give off subtle popping sounds as it expands and contracts? I just started using a new bathroom I renovated and it sounds like water is dripping on the ceiling and/or wall below the shower upstairs but I have let the shower run for an hour straight and poked holes all over the wall and ceiling looking for moisture and I can't find a trace of it. Am I going crazy?

I guess my question was answered by the other post regarding ABS and movement due to temp. changes.....

If it sounds like the pipes are hitting something, then you need to secure them differently or insulate them.

If it sounds like water is dripping, you might just have a leak.

Verdeboy said:

If it sounds like the pipes are hitting something, then you need to secure them differently or insulate them.

If it sounds like water is dripping, you might just have a leak.

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The weird thing is, I really only hear the sound when the hot water is running to the shower. When I run only cold water through the drain, I can't hear the sound. I've run at least 100 gallons of water through the drain and I can't find a trace of any leaks. I guess I'll leave it alone for a while and see if anything obvious pops up.

KSHandyMan said:

The weird thing is, I really only hear the sound when the hot water is running to the shower. When I run only cold water through the drain, I can't hear the sound. I've run at least 100 gallons of water through the drain and I can't find a trace of any leaks. I guess I'll leave it alone for a while and see if anything obvious pops up.

Click to expand...

That would be because of hot water expanding the pipe!

The pipe expands in all dimensions, and when it chafes against its supporting structure, you get the popping sounds. I've got a 20' run of CPVC tucked under the toekick around my kitchen cabinets (it was a replumbing job with no other practical routing) and it pops every time we run the hot water. A long run of CPVC in the attic gets about 3" longer when it heats up, as I remember. One of copper's advantages is its relatively low coefficient of expansion; ABS is about the worst there is:

Copper 9.3
PVC 29
CPVC 34
ABS 55

The numbers are in inches/inch/degree F*10^-6, from http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html. The same website offers a convenient Excel spreadsheet to calculate expansion at http://www.engineeringtoolbox.com/docs/documents/283/temperature_expansion_pipes.xls. If you do run a long run of pipe which will be subject to wide temperature variations, you need to be careful to allow room for the pipe to expand, and maybe provide a slippery surface for the pipe to move on. Otherwise, you might get popping noises...

I realize it's probaly because of the heat but only by experimenting did I come to that conclusion. It really sounds like water droplets hitting drywall but after having the water running off and on all day and not seeing any sign of moisture I suppose I'm comfortable with just chalking it up to expansion.

It's really not that noticeable unless you are in a downstairs half bathroom which is directly below the shower and which also happens be the location that the 3" stack runs down the outside wall of the house. So, I'm just leaving it alone. No since trying to fix something that really isn't that much of a problem.

Thanks for all the replies. And, that's really interesting about how much ABS expands. In the future, I'll be more conscious of how other materials come into contact with it.

It's nice to hear from another conscientious handyman.

We get bashed quite a bit on this site. But it's better to be a handyman who is willing to learn and improve, than a tradesman who thinks he knows everything.

Verdeboy said:

It's nice to hear from another conscientious handyman.

We get bashed quite a bit on this site. But it's better to be a handyman who is willing to learn and improve, than a tradesman who thinks he knows everything.

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I love handymen! A great source of income fixing their mistakes!

Funny, I feel the same way about plumbers.

most likely the holes penetrating through studs and or floor are too tight.The "dripping"sound you hear is the pipe rubbing the wood as it expands and contracts

The irony here is that the drain stack that is causing the issue was put in by a professional plumber when the house was built. So, I guess you could say that, just like handymen, there are good and bad.