Lost a 20# tank over the weekend. First leak in a very long time. First guess is one of the "permanent" brass/rubber o-ring gaskets that you screw in with an Allen wrench. Looks like I got a little aggressive last time swapped tanks and damaged the o-ring. Guess it was good since that tank was about 3 weeks from recertifying and another 10# need a fill.
I have about 40' of new CO2 line to replace what I have now. Would have sucked if the leak started after that and I had to check every connection.
Guess I was due,