Pipes banging when sprinklers are on

[panchor]

I just have a water heater installed and since then, every time i turn on my sprinklers or they change zone, the pipes in my basement near the water heater start banging for a few seconds. The plumber also installed an expansion tank next to the water heater.

I noticed that if I close the valve that feeds water to the water heater, the banging does not occur. So the problem is either the water heater or the expansion tank.

Does anybody know how to fix it?

Thank you

[HayZee518]

check the expansion tank for a leaky bladder. there is a rubber bladder inside that is pressurized to around 40 psi to absorb the water hammer.

[panchor]

I checked the expansion tank and it seems it is working. The pressure is at 55.

[manhattan42]

The problem is not the weater heater nor the expansion tank.

The problem is with the quick-closing valves on the sprinkler system.

Each quick-closing valve requires a water hammer arrestor.

You need to install one on the water line(s) that feeds your sprinkler system.