Booster Pump of Water Heater Hot water pumps constitute a complete range of 3-speed circulator pumps, available both in 50 and 60 Hz. The pumps can be used in both open and closed systems. HH & HW pumps are of the canned-motor type, i.e. pump and motor form an integral unit without a shaft seal and with only two ceramic bearing for sealing. The bearings are lubricated by the pumped liquid.