I installed this recently and it works very well. You should not expect it to be able to heat up a tub of cool water, but it will maintain the temp of a tub full of water for as long as you run the pump. What I really liked was the slightly lower power than others. Because of the lower power one can reasonably put this heater on an circuit that has other outlets on it as well. For a high power heater one must use a dedicated circuit. This heater comes with several different adapters; I expect it will fit almost any tub that is designed to take an in-line heater.