QUOTE (Stephen T. @ Sep 21 2009, 04:27 PM)

Doing propane as a maintenance man, at remote cabins, we always used soft copper tubing, flare fittings and heavy duty flare nuts, designed for propane lines. The propane delivery company would come out and pressure test our lines, and were very happy with my work. At least in Oregon, this was the proper way to do things. No form of tape or pipe thread compound is needed on proper flare fittings. It's a different story on threaded joints though.
Steve
I see that the problem here is the fittings and not the tubing, I haven't seen the nuts split like that before. The only thing that comes to mind is overtightening. However, when replacing the lines ....
PLEASE NOTE!!! Soft copper comes in two common types at your typical mega hardware store. One suitable for gas and one suitable for water. The gas line is heavier guage and is clearly labeled on the box. Also it costs more. Also, a proper single flaring tool should be used, which is usually available at the same store.