Watts heat H2O hot water recirculation system provides hot water to a faucet or shower instantly, eliminating water waste caused by waiting for water to heat up. This pump offers quiet, maintenance-free operation and includes a programmable timer that can be set to activate the pump only when needed or set it to run 24-hours a day. The device uses the pump at the water heater and a patented under-sink sensor valve to create a pressure differential. The pressure differential allows the cold and cool water in the hot water supply line to bypass into the cold-water supply line at a low volume through the thermostatically controlled sensor valve, keeping the water in the hot water supply line at a no wait temperature throughout the home. Caution: This system is not designed for tankless water heaters.