Natural gas is a little lighter than air and a smallish molecule. I'd say an hour was more than enough for a couple of metres of 22mm.
Don't really want to go bang, when I get the blow torch going.
Plumber I once new said he generally cut, then lit the end!! I guess that's fairly safe if you can point the cut end into open space or against some masonary and you do it immediately before an explosive gas/air mixture has chance to develop. I don't think I'LL bother though!
Okay, I'll give it an hour. Perhaps put some tubing down it and blow.
-- Mike W
The larger the diameter of the pipe versus the length, the more easily will the gas come out to be replaced by air, especially if the pipe slopes up to the cut end. I would guess at two or three minutes for it to be clear of gas and safe to solder a two meter length.
Thanks, I was expecting a good finger wagging. Thing is I've done it before, just can't remember how long I left it, and I guess I'm getting more cautious. Last time I put a cap on the end of 20ft of 15mm, then somehow didn't blow anything up since how was I to purge the pipe? This time that same bit of pipe gets a valve!
-- Mike W
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