Well in an automotive install you'd have a shutoff valve at the tank multivalve that you can physically screw shut, and a solenoid valve to allow fuel out to th

Well in an automotive install you'd have a shutoff valve at the tank multivalve that you can physically screw shut, and a solenoid valve to allow fuel out to the line. Then up front there will be a filter and safety valve with another solenoid valve, and finally a solenoid on the vapouriser too. If I want to take a vapouriser off I'd just unplug the solenoid for the safety valve, start the engine, let it cut out, and then unscrew the pipe. Similarly if I wanted to work on the safety valve, I'd shut the tank off and let it empty the line running to the back of the car. The gas lines we use now are thin nylon with a tough PVC jacket over them, about as thick as a pencil (6mm inside bore) and flexible enough to tie your boots with ;-) It's a long way from stiff fragile copper line.