Nofault Heater Assembly, 1.5kw/6kw Part Number: 73790 No-Fault PDR Titanium Heater comes with thermistor o-rings. This model has a double-pass design, which helps with the heating of the water. A replacement for all Hot Spring Spas, 1995-current, that are 1.5 / 6kW. Hot Spring Spa Supplies carries spa fragrances, air & water valves, control systems, filter accessories, lights, cleaners, pumps, thermostats, and more for virtually every hot spring model.