Because all waterways are corrosion-free copper and bronze - not aluminum. And, SpaPak features large size, heavy duty Incoloy heating elements that lasts far longer than ordinary water heating elements. Troublefree Because SpaPak has extra quality and safety built-in - a pressure switch to prevent operation without water flow, a high limit temperature control to prevent overheating and a dependable quality thermostat. Easy to Install With a compact design that fits into small spaces. Standard size, full flow 1-1/2" inlet and outlet connections are conveniently located. External current leak protectors are not required. Two Year Limited Warranty Against defects in materials and workmanship (see written warranty for details). In addition, every SpaPak is thoroughly tested before shipment.