Eternal GU195S Condensing Hybrid Water Heater, 19.5 GPM Ultra low emissions (1ppm CO) leaves almost no carbon footprint and is safe 98 percent+ Efficiency saves cost, exceeds Energy Star standards, and qualifies for Tax and LEED credits 2-Inch PVC up to 35-Feet or 3-Inch PVC venting up to 100-Feet Thermostat and Flow Activation is compatible with WaterSense fixtures Up to 19.5 GPM of unrestricted flow, 199000 BTU's Max Input