I have a continuing water hammer problem since getting a new front-loading washer a few years ago. When the washer valve closes, there is a single thump heard in the second floor shower. The washer and the shower are the last plumbing devices on their respective lines. I installed arresters on the hot and cold water shut-off valves for the washer, which helped for a few months only. The arrester manufacturer replaced them under warranty, and suggested that I add two more arresters to the back of the washer (for a total of 4 arresters). I did this, and again only had success for several months. I tested the water pressure at the washer shut-off valves recently, it was 45 psi. I have limited access to the pipes to the shower, and they do not appear to be loose. One other thing that I have noticed: when I turn ON the hot water at the vanity faucet in the same bathroom, I hear the “thump” in the shower wall. This only happens with the hot water, and only when the hot water valve is opened (as opposed to the thump created by the washer, which seems to occur when the valve closes.) No other faucets or appliances cause the noise. I have had two different plumbers here in the last year for other reasons, but neither could suggest a cause or solution other than replacing the arresters. If anyone has a suggestion, I would greatly appreciate it. Thanks in advance.

One by one, turn off isolation valves in that bathroom and see if the problem goes away.

How can you see those water lines behind the shower?

- - - - - -


Everything in Plumbing can be repaired or replaced.

Since it happens in the shower when a hot water faucet is turned on, the implication is that it is the "balancing spool" compensating for a sudden drop in the hot water pressure, while the cold stays at a higher level. Check for something compromising the flow at the water heater.



Edited 1 times.

Thanks for the replies. As to how I can see the shower pipes: There is a garden tub adjacent to the shower stall, and there is a louvred vent cover in the tub enclosure close to the end of the tub that is near the shower. When I remove the louvred cover, I can see the plumbing that serves the tub, as well as the lower 2 feet of the shower plumbing. I can’t see any higher, but when I grip the pipes and try to move them, they seem to be affixed solidly. (Not sure why that louvred cover is there, but it is convenient.)