The Ruud Spa-Pak Indoor/Outdoor Electric Spa Heater features headers that prevent rust stains from harming your pool or spa’s surface, giving you years of trouble-free swimming pleasure. The cast brass headers are connected with an all copper water tank. This spa heater also comes with a built-in device to prevent overheating. In the event the heater is energized when the water flow is insufficient, a resettable high limit will prevent the heater from operating in an unsafe condition.