This 240 volt, 11kw inline Coates spa heater from Coates Heater Company can be used for residential spas between 250 and 600 gallons. It features a stainless steel tank that is designed to optimize heat transfer by directing the water flow over the incoloy elements efficiently. This indoor/outdoor heater also features a built in pressure switch that prevents operation when there is no water flow and allows operation at flow rates between 15GPM and 80GPM. There are 1-1/2 x 2 inch PVC union connections. Other technical specs: 1 phase, 46 amps, 37,530 BTU's/hour.