Active Aqua AAPW550 Submersible Water Pump, 550 GPH, 33W, 6 Ft Cord

A chiller without a pump is a cold box that nothing flows through. The AAPW550 is the middle of the three pumps the Active Aqua chiller’s listing names: 550 GPH (2,082 L/h) from 33 W, with a magnetic drive, a ceramic shaft and a foam filter over the intake. It sits on the floor of the tub on suction-cup feet and pushes water up a hose to the chiller.

It is a hydroponics and aquarium pump, and the listing says nothing about running in water with a person in it. Treat it as equipment that works between plunges: unplugged before you get in, plugged back in when you are out and dry. Its listed maximum lift of 5 ft (1.5 m) is also enough to empty the tub into a utility sink.

Tip: Keep both hoses as short as the layout allows – every extra foot of tubing costs flow, and the chiller wants at least 396 GPH.