I have a propane leak, found it when I got home from my last trip last year, been lazy on getting it fixed. I have dual tanks and the full one leaks, so it's after the tanks, somewhere in the line to ...
I had a hard to find leak that was in the middle of the copper line under a wooden board that the heater mounted to.......one mounting screw was sticking out by 1 mm and was tapping that line for 14 years till it made a hole.