The keg is a wonderful invention, but it’s of little use if you can’t get beer out of it. That’s why we have couplers or, in the case of homebrew kegs, disconnects. These are the hardworking unsung heroes of every draft system that attach to the keg, delivering gas and pulling out beer.
Commercial couplers use the Sankey system, which does both jobs with just one piece of hardware. Homebrew kegs, however, use separate disconnects for liquid and gas lines. And because these old soda kegs are the product of a diverse varied history and recent innovations, there are three big questions to ask yourself for when buying new disconnects.
1. What kind of keg(s) do I have?
Ball lock or pin lock? Ball lock kegs were originally developed for Pepsi-Cola, and pin-lock kegs have a Coca-Cola pedigree. The two systems are, as you might suspect, as incompatible as the two soda companies that used them. Pin lock kegs are easily identified by the small pins that protrude from the posts: Three pins on the liquid post and two on the gas post. The only distinguishing feature on ball lock posts is the small notch in the corners of the gas post.
2. What kind of disconnect do I need?
I usually buy liquid and gas disconnects in pairs so that I have an equal number of each, but every now and then, you may need to buy one on its own (if, say, you manage to break one). In this case, make sure you buy the right kind. The golden rule is “Gray for gas and black for beer,” and this typically holds true for both ball lock and pin lock systems. However, there are exceptions, such as stainless disconnects, so do take the time to double check that you’re buying what you need.
3. Do I need a disconnect with a hose barb or threaded connection?
Hose barbs attach directly to a length of tubing and are meant to be left in place. Threaded connections screw into a ¼" MFL swivel nut and are easily removed. These connections, like the ones shown at top, are great for brewers who maintain a diverse fleet of ball lock, pin lock, and commercial kegs. If you’re strictly tied to one system, though, the barbed connections are just fine.
Perhaps one day manufacturers will decide on a single type of system. But if cell phone chargers are any indication, we probably ought not hold our breath.