WILO-Star 21F circulating pump 1/12 HP for solar domestic hot water heating. Three speed operation and stainless steel construction with cast iron volute. Standard flange mount. Suitable for closed loop systems. Medium head performance for all closed loop systems. Maximum head 21 feet. This pump motorhead (use the existing volute) will replace Wilo pumps in Heliodyne HPAK heat exchanger pump stations, as well as the Wilo Star 16 in Schuco & Caleffi pump stations.