Model-PTU-3 Pump and Tank Unit was designed for use with thermoelectric cooling and heating stages. It provides a convenient reservoir of cooling water when a stage is operated in the cooling mode for an extended period of time in a location which has no source of tap water nearby to cool the hot side of the thermoelectric heat pump. The reservoir tank holds seven gallons of water, which is adequate to run the smaller stages like the TS-4 series Thermal Stage or the BFS series 3 or 5 Freezing Stages for up to eight hours and a larger stage like the BFS-30 for up to four hours. Water is circulated using a quiet 1/25 horsepower single phase motor and magnetically driven pump - so there are no rotating seals to leak or replace. Self sealing connectors are used on the inlet and outlet water connections to prevent spillage. Ice cubes may be added to the tank in order to extend the operating time or reduce the lowest temperature to which the thermoelectric stage can cool. A switched accessory outlet on the read of all thermoelectric controllers and power supplies is used to power the pump so water starts flowing immediately when the controller is turned on.