I was enamored by the self-serve sparkling water tap at Pizzaria Farina, and decided I must have one of my own. I began researching these things like crazy, and eventually decided I would have to settle for a slightly more manual contraption, at least for now. All of my research led back to Richard Kinch's website, who has posted a wealth of information on this topic, from theory to history to implementation.
I got a 20lbs tank of co2 from Dan's Homebrew Supply along with a regulator, hose, and connector for 2 litre PET bottles. The deposit on the tank is pretty steep, but a refill is only $20 and makes 500 bottles of seltzer.
The process is pretty simple:
This setup is featured in a silly beekeeper video!