Just had to do it myself to a Maibock last Sunday. It was great going into the keg. But after time in the keg, it went way south - foamy (although it had been purged, but never carbed), flabby, too dry, acidic, etc. I soon realized the keg had developed what looked like stubborn rust on the bottom and, try as I might, I can't get it to removed. It must be harboring some bacteria. Will canibalize it for parts, then send it to the recycling tomorrow.