So, I kegged 6 beers one night and the next day put them on c02. Two were acting funny though, one wasn't holding pressure (still need to fix that), the other was, but when I turned c02 on it, it would sound weird. After trying to connect the beer tap weeks later, I discovered they were switched (SOFAB!!), so when you hear a weird sound like c02 is coming from the bottom of the keg and not the top, check your lines aren't switched. HAHA. I'll never forget that sound.