We've traced our water hammer to the hot water side. Closing the water supply to the water heater eliminates the hammer. The hammer is triggered by shutting any valve throughout the house as well by flushing any toilet; but the sound is loudest right at the water heater.

Our water heater is equipped with an expansion tank, and the pressure gauge downstream of the pressure regulator indicates 70psi, so we're figuring the fix is the installation of an arrester. Should the arrester be installed on the hot water pipe that exits the top of the water heater? If not, where?

Hi Jffnszn

More likely will be that the water heater has DIELECTRIC nipples with heat trap balls in them. Remove the nipples and replace with new dielectric nipples without the heat trap balls in them... ;)

Mark