Search for the water hammer in master bathroom. Sounds are coming from within the shower wall like a loose water line. Opened up wall behind shower to inspect water lines. All lines were tight and found nothing loose as we continued to test for water hammer noticed the sound was coming from the shower valve area. Capped off hot and cold water lines to isolate the shower valve. Ran water in the bathroom and quickly closed tub valve and the water hammer disappeared ruling out loose se piping. Problem is the shower valve cartridge failed and needs to be replaced. Shower valve is an Amazon valve from china and no replacement parts are available. Client ordered new shower valve to use for replacement parts if problem still occurs after replacement then the walls will be opened and a new valve will be installed with a transfer for handheld ex: Moen, Kohler or another brand that has replacement parts. Went to turn off water to house to replace PRV valve for irrigation and the w