Noritz NRC98-ODNG Outdoor 9.8-GPM Natural Gas Condensing Tankless Water Heater Super Efficient - DOE Energy Factor of 0.94 (Propane) 12 year warranty - Longer coverage than competition, 12 years on heat exchanger, 5 years on parts, 1 year labor Installation flexibility - PVC or CPVC piping. Built-in PVC adapter for either 3" or 4" PVC or CPVC Stable Temperature Control - No need for a buffer tank to stabilize temperature. Therefore, no stand by heat loss Low Pressure Loss - Norirtz provides a better shower experience across a wide range of water pressures