What would cause the water pipes to rattle very loudly but only when the hot water is turned on either in the kitchen sink or washer and sink in washer room. It doesn't happen when cold water only is turned on or if any other faucet/water is turned on anywhere else in the house.
Loose pipes or air in the lines. If you have copper lines you could just be hearing the rattle of the pipes jumping around. Fairly normal for pipes to want to move when being used but is not a problem as long as the pipes are secured and cannot move around.
Also, could be air trapped in the lines causing water hammer.
if you've got room in the cutout for the pipes to slide some pipe insulating foam over that rattler, give it a try. might do just enough to stop the noise.
if not, you have a loose or missing pipe hanger, or might need to open some wall up and install a water hammer arrester. you can make them with a reducer, a length 8-12 inches or so of pipe a size or two larger, and a cap on that pipe. pre-assemble that, and connect with a tee to the existing pipe.
sig: if this is a new economy, how come they still want my old-fashioned money?
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