Noritz NRC111-SV NG Indoor/Outdoor Condensing Tankless Natural Gas Water Heater, 8.4 GPM 199,900 BTU 0.5 GPM Minimum Activation Flow Rate, Max Flow Rate 11.1 GPM Self-Diagnostic Onboard Computer System 93% Thermal Efficiency 3" - 4" PVC Venting Allowed (PVC Adapter required). Outdoor- No Venting Required