Legend Tankless Water Heater Isolation Valve Kits are intended for installation onto tankless water heater cold inlet and hot outlet connections. Each assembly features union connections, full-port, positive-shutoff ball valve design and integral drain valves with capped hose thread connections. They are available with 3/4 or 1 FNPT union water heater connections, with 3/4 in or 1 in FNPT or sweat supply and return line connections.