Drain tapping noise

oddsmell

oddsmell

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I tried searching and didn't come up with this so here goes. When "anything" drains in the house (1st and 2nd floor) I hear a tapping noise. No, it doesn't have anything to do with hot or cold water expanding or contracting, it only happens when something drains. If someone is taking a bath the tapping starts when they drain the tub, not when they fill. Also if it is a bath, then drain, the tapping starts and last for about 20 secs, starts slow, picks up speed then stops even though the tub is still draining. Any thoughts? Thank you for your time.
 
I could be wrong on this but thermal expansion/contraction of ABS piping is minimal and would require quite some time to actually "move" any significant amount. I'm going to check this out if I can find an engineering handbook. Even aluminium would only move a few thousandth of an inch if it was heated by 50 degrees or so. I'll look into this, thank you kindly for your reply.
 
You are wrong, it IS the ABS piping rubbing against something as it tries to expand. If a hole it goes through is already tight, how much do you honestly think it needs to move before it makes noise?
 
How about air being sucked through a trap on a sink, etc. Try filling the sinks and see if the noise continues.
 
Normally such noises are produced where a pipe is touching where it penetrates a framing member.

The simplest diagnosis would be to run water through it that is the same temperature as the rest of the room to verify that the noise does not occur. The noise would take place when the water is hotter or colder.
 
The linear coefficient of thermal expansion for ABS is 41e-6 in/inDegF. So, a 50 degF rise in temperature would cause a 10 ft length of ABS to expand about a quarter inch.

Often, plastic drains are tightly (improperly) constrained by framing members or holes, and the type of sound you are experiencing is commonly due to thermal expansion.
 
Particularly on a horizontal run, it's not quite that simple since the fluid is only traveling though the lower portion of the I.D. of the pipe. This in effect causes the pipe to slightly bend each time that there is a notable change in temperature.

I have had to cut and file existing holes in framing where the pipe was pressed against wood and making all kinds of noise.
 
Thanks to all of you for your repies. I kept looking for some sort of leak that I couldn't locate. I feel "slightly" better knowing it's just a pipe rubbing. I'll still have to find it and if it's not to $ look into fixing it. Again, thanks to everyone for your input and help, appreciate it.
 
When heated water goes down the drain, it expands the pipe. As the pipe cools back down, it returns to it's original size.
What you have is expansion and contraction of the pipes as they fit in the holes in the wood studs. If the hole was slightly crooked, it's more likely to make the ticking sound as the pipes cool.
I've had to go back on some service calls and cut out wood that was rubbing the pipe.
 
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