GQ-C2857WS-FF-US-NG Noritz 180,000 BTU Residential Indoor Condensing Direct Vent Natural Gas Tankless Water Heater Offering a maximum input of 180,000 BTU per hour, the GQ-C2857WS Tankless Water Heater is designed to fully meet the domestic hot water needs of northern residences with two bathrooms and sourthern homes with three baths.Energy Factor of 0.92 (Natural Gas) 0.94 (Propane)Flow rates from 0.5 gpm up to 9.8 gpm12 year warranty on heat exchanger5 year warranty on parts1 year warranty laborPVC or CPVC piping. The less costly, zero clearance plastic piping enables longer vent runs up to 62 linear feet. Built-in PVC adapter for either 3 in or 4 in PVC or CPVC.Stable Temperature Control - No need for a buffer tank to stabilize temperature. Therefore, no stand by heat lossNorirtz provides a better shower experience across a wide range of water pressures.