Less500
Thanks for the response. Actually, I think we eliminated water hammer. Put on arresters, but nothing has changed. The water supply lines serving that bath on 2nd floor run through the floor, or what would be the ceiling of the first floor. The noise appears to be clearly coming from inside the wall, which only houses those drain pipes. It’s definitely not toilet—it’s the shower, which stops when shower stops, and separately, the sink, which begins when sink is on, lasts a little while longer. Many here thought it was the PVC pipe expanding, which seemed logical, and the pipe is about as fat as the wall is thick, so it could be knocking into wall??
