Grundfos hot water circulating pumps. Enjoy the convenience of instant hot water in your home and minimize the waste of energy with a hot water recirculation pump, insulated piping, timer, and aquastat. Hot Water Circulating Pumps Kits For System Without Return LineUses the existing cold water line as a return line eliminating the need to install a new recirculating line. Hot Water Circulating In-Line Pumps For Systems With Return LineThe hot water side of each fixture (faucet, shower or other appliance) must be placed in a continuous loop by connecting a hot water return line from the last fixture to the water heater. Frequently Asked Questions