Thanks for the replies I'm convinced now that it is just expanding and contracting. I might try to stick some cardboard or something around the pipe to see if that helps. I was more concerned than annoyed. If this is my biggest problem in the house then I'm doing pretty good, knock on wood. My last house was pretty old and had copper pipes. In the garage the pipe that drained the kitchen sink wore through and leaked. Nothing J.B. Welding didn't fix.