Rebuilding residential manifold on existing 1" main to two 3/4" Superior ASV's with actuators. Fire and shut down system, pipes rattle under kitchen, crank on newly installed ball valve, less hammer but noticeable. Explain to client possible causes. She explains during construction, contractor forgot to plum for wet bar in the ktichen. Under sized pipe me thinks. Fire up and shut down system, 1/2" copper lightly rattles a homemade bottle of schnapps. Clients husband pours shots of schnapps all around. No more water hammer. have met the most interesting folks in this business!!