I just hooked up the gas line to the 75000 BTU Mr. Heater unit and got it going last night. I went to a contractor supply house and bought a 5' flexible gas line. The description read "7/8 60IN SS GAS CONNECTOR" part # FL 30-3141-60, there was a 3/4" male end on one side and a 1/2" male end on the other. I checked with the inspector and he said either flexible pipe or black pipe was fine. The flexible pipe must be rated for 75,000 BTU or higher (the rating gets smaller the longer the pipe gets).