How To Outstupid The Best In Safety Devices (LPG)

Spit into the disposable bottle valve? Kayteg1 when I was refilling butane bottles for the beach campers down here I had to go through an elaborate process.

Refill the bottle. Check for leaks. If there was a leak I froze the bottles, took an ice pick and re-seated the bottle's valve then re-checked. That cannot be done with propane and the average freezer. I ended up buying brass caps for my own bottles. The caps had cut out inner-tube discs for seals.