We recommend adding 15-40lbs (7-18kg) of ice to the Ice Tub per session depending on the initial water temperature. The amount of ice needed highly depends on your tap water temperature, the climate you live in, and how cold you desire it to be. If you live in colder climates, adding ice may not even be needed. Since the tub is insulated it will keep the water cold for longer, and you may therefore not have to add as much ice after the first time.