Originally Posted by kerant
How exactly do you purge the empty keg?
It's going to be very tough to get all the regular air out of that large of a space, but just fill it with CO2 when it's all sealed up, let it sit for a second or two then pull the relief valve on the top of the keg.
Personally, I've never found this that helpful, because as I posted in another thread, CO2 is more dense than Oxygen, but not by much, so any disturbance usually just mixes things back up anyways. I always find it best to purge after the keg is full and there is very little headspace left. This way it's more likely you are just plain pushing the old air out and replaing it with CO2. Not that you can't do that empty, it just seems like a waste of CO2 to me, for the little benefit it might give.