I have talked to a few people with all different answers so I thought I would open up the discussion here. I have a 2005 Florida home, The hot water pipe leaving the hot water heater going into the bedroom closet wall is making a noise. A clicking/clunk like noise. At first it made a rapid click right after turning off the water. Now it does it during the water running, after the water running, and the same noise can be heard hours after not even running the water only difference is the noise is just one clunk every 5-10 minutes. The pipe is PVC. I do not have an expansion tank on the water heater. And there are water hammer valves installed around the house like the washing machine, and under the sink from what I have seen so far. The noise was liveable during just water operation, but trying to sleep and hearing that is starting to make me crazy. People have said its just the hot water in the pipe and its normal, some say add an expansion tank. Any advice would be great, thanks.