Recirculating hot water pumps reduce waste by returning water that has cooled through the cold water pipes to the water heater. The installer places the pump at the last tap on the hot water circuit. A temperature sensor starts the pump when the water reaches the set temperature.
In homes without a water heater pump, several gallons of water are wasted daily when occupants turn on the tap and wait for the warm water to reach the tap. The waste increases the demands on the water provider and the wastewater treatment plant. Recycling water to the water heater provides the convenience of instant hot water while reducing these demands. Using the cold water pipes to return the water to the tank makes installation easier and less costly in existing homes, but users sometimes notice an increase in cold water temperatures.
A second method of installation of a hot water pump uses a dedicated hot water return in a circulating hot water system. With this method, the installer places the pump anywhere after the last tap, even on the water heater. The circulating system is more expensive to install, but it maintains the water at a higher temperature, and it eliminates the increase in temperature of the cold water. Since the circulating system requires a dedicated return line, it is less common when retrofitting homes.