A recirculating pump brings instant hot water to any room in the house. There are two types of recirculating systems, closed systems and open ones. It reduces undo stress on the tank caused by the thermo shock of new cold water entering the system, by tempering this new water with the returning warm water. Recirculation decreases the amount of cold water that enters the system, and that results in much less condensation and less thermal stress on the tank. Yet the actual circulator requires a minimal horsepower motor in the range of 1/12 or 1/16 hp, or just enough to keep the water moving.