Hot water heater recirculators return cold water from the pipes to the water heater to prevent water waste. With these units in place, the water in the faucet remains hot, and the cold water is preserved instead of going to waste.
The best type of recirculating pump depends on the type of water heater. Demand systems heat the water in the pipes to a set temperature and the pump stops. When the temperature reaches the lower limit, the thermostat starts the pump to maintain the hot water within the set range. In open loop systems, the water circulates continuously.
Some tankless water-heating systems, such as those by Rinnai, have a built-in recirculating pump, while other units require the owner to install a pump. Some systems also have the ability to learn a family's usage habits and circulate water when members are most likely to use it. With storage tank systems, the pump moves the water through the tank to keep it hot. With either system, the water is hot any time the tap is open.
The average family wastes 15,000 gallons of water annually while waiting to empty the cold water from the hot-water pipes. The recirculating system reduces water consumption by 10 percent in the average home; however, the system increases energy consumption.