You’ve likely see a WunderBar or bar gun – a single dispenser for 4 to 12 different beverages. Bartenders use them to dispense many of the mixers they need from water to club soda to cola.
A typical modern bar gun is connected to a syrup / water / CO2 mixing system. A long time ago, the soda came pre-mixed in 5 gallon stainless “kegs” and the bar gun was just the centralized dispenser.
The DIY home bar can have something similar! In place of 5 gallon kegs, we will use 2 (or 3) liter bottles.
The system consists of a CO2 cylinder and pressure regulator, a distribution manifold, the bar gun, some tubing, and a bit of DIY to create a fitting for soda bottles.
The trick is to creat a custom head fitting that lets CO2 into the soda bottle through one tube and forces the soda out through another tube.
The head part consists of a “street tee” fitting with two NPT-to-barb adapters.
To make the unit, a 4″ length of brass tubing is bonded (soldered or using JB Weld) inside one of the NPT adapters. Next, a brass or copper washer is bonded to the threaded neck of the street tee. The unit assembled with Teflon tape so the brass tube runs down the center of the street tee. A hole is drilled into a soda cap just barely large enough for a snug fit when the threaded neck of the street tee is inserted. A neoprene washer is sandwiched between the washer on the street tee and the soda cap. Finally, it is all tightened together with a nut on the inside of the cap, threaded onto the threaded neck of the street tee.
NOTE: If you use 1/8″ NPT hardware you will have plenty of space inside the soda cap. If you use 1/4″ NPT hardware as in this example, things will be tight and sanding if grinding down the NPT nut will be necessary (which is why the nut in the picture looks round with two flat sides).
Someone on the Internet sells plans for $12 this setup. I found all the details by doing an Internet search for “soda bottle mini keg”.
The setup isn’t cheap (the parts for just one soda bottle head fitting is $15US). So, unless you are doing for the experience of building something or you must have all the cool gadgets, I’d just stick to having soda bottles behind your home bar it in you personal Pub Shed.