Our upstairs master bathroom makes a noise in the wall that sounds like dripping. The noise only occurs with hot water and it is located in the drain pipe not the supply line. I know this because I plugged the sink and filled it with hot water. i then turned off the water and when I drained the hot water it started making the dripping sound again. I opened up a small area in the wall and there are no signs of leaks. My best guess is that it is thermal expansion. If this is the case why am I not having this issue anywhere else in the house? Would rubber expansion joints help the situation? The pipe is solid black plastic not PEX. It is rigid and you can sort of feel a small vibration when it makes the drip noise. My theory is that the expansion joint would decouple this eliminating the vibration. Does this theory make sense? Has anyone else experienced this type of problem? If so, how did you resolve it?

Hello, Have had a pinhole leak this year, and also a few years back, so started looking at my Copper house water plumbing a bit. Noticed several areas with that bluish-green coating on it. a. Is this indicative of a pinhole leak developing ? b. what actually is this bluish-green "stuff" ? c. Is it a reaction of the Copper with the outside air, and thus developing on the pipe's outside, or it coming from the inside ? d. Interesting in that I see it in the middle of a run, here and there, so it's unlikely that it is caused by any soldering flux residual. I do also see it at joints, and am wondering if it is caused, here, by a soldering flux residual ? Any thoughts on the bluish-green stuff, and pinhole leaks would be most appreciated. BTW: how common are pinhole leaks in older (around 35 yr old) homes ? Thanks, Bob