Random Zone-Change Water Hammer in 5-Zone System

A homeowner experienced loud pipe rattling during zone changes (not on the last zone) after a bathroom remodel and blowout-port repair. Opening a faucet during transition caused water to be sucked from it. Pressure tested at 88 PSI previously. Contractors gave conflicting opinions.

Start by identifying valve brand (Toro, Rain Bird, etc.). With the system running, slowly close the main irrigation isolation valve ¼ turn—if hammering stops, flow velocity is too high. 88 PSI is elevated; a pressure-reducing valve may help. Also check for air in lines and ensure valves close slowly. The remodel may have altered piping dynamics. Systematic testing isolates the cause: excess flow, pressure, or valve speed.