Natural gas tankless water heater with electronic ignition delivers over 7 GPM at (45 F.) enough to run up to 3 major applications (showers) at 1 time. Built-in power vent allows for vertical or horizontal vent termination up to 26'. Exhaust vent size: 3'', for horizontal vent termination must use the model No. AQ3ES vent kit. Vertical vent must use single wall gasketed stainless steel pipe, please contact vendor for drop shipment pricing on pipe. Combustion air pipe size: 3'' rigid PVC aluminum or galvanized. Unit has modulating gas valve from 19,900 to 199,000 BTU. Gas connections are 3/4'' Male NPT, water connections are 3/4'' NPT, Natural gas pressure: 4'' WC/Max. 14'' WC, water pressure: minimum 30 P.S.I., maximinum 150 P.S.I. Solid copper heat exchanger, stainless steel burners, computer controlled operation, 120V. plug in to operate computer and power vent. .82 energy factor, thermal efficiency 82%. Minimum flow to activate burners is .65 GPM. 12 year warranty on heat exchanger, 2 year parts warranty. CSA listed.