Ah, I had this image of someone trying to blow co2 into the tube with their co2 setup and thinking it would be purged. Guess I didn't think that one through much further. When I ferment in kegs, I push sanitizer through my jumper until it's all gone, then there's nothing but co2 in the line, and transfer the beer from keg to keg. Works great, but I like fermenting in buckets right now as I can skim off the braunhefe crap, which I think truly makes a difference. Can't do that in a keg; not very easily anyway...