STAIRS HW series residential and light commercial hot water circulator pumps constitute a complete range of 3-speed circulator pumps. The pumps can be used in both open and closed systems. HW pumps are of the canned-rotor type, i.e. pump and motor form an integral unit without a shaft seal and with only two gaskets for sealing. The bearings are lubricated by the pumped liquid. This pump has 130mm or 180mm port to port dimensions to be chosen.