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.
Cornelius brand bar gun and CO2 distributor
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.
custom brass soda bottle dispenser head
The trick is to create 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 or 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.
UPDATE #1: if I were to build these again, I would switch to 1/8″ NPT and find 1/8″ NPT to 1/4″ ID barb fittings. The 1/4″ NPT fittings are fine but getting a 1/4″ NPT fastening nut inside a soda cap requires it to be ground down considerable and for the through-hole to be perfectly centered in the cap. The change to 1/8″ NPT fittings would not change the flow volumes. It would tighten up the tolerance for the copper tube passing through the street tee fitting which would mean it would need to be perfectly centered. For this reason, I would switch to JB Weld rather than soldering the tub into the NPT adapter fitting.
UPDATE #2: It works fine for non-carbonated but not for carbonated sodas. As I suspected, the small channels within a post-mix gun cause nearly all of the carbonation to be forced out of the soda. I tried several CO2 pressures and the best I could achieve is perhaps 25% carbonation in the served glass. This solution is fine for ice tea, water, lemonade, etc but not for carbonated soda. Oddly enough, it would work for liquors by setting the pressure very low. Of course, you’d want to use nitrogen rather than CO2. You might end up with a tiny bit of cross flavor but it would be very small and easy to solve but leaving water on one line and a quick flush between cocktails. Interesting thought: you could use this postmix gun setup and serve any of the cocktails which do not used a carbonated liquid. Or just learn the fancy moves from the movie Cocktail. There are a few suppliers still selling new premix guns. A 5 (or 7) button new premix guns is about $170US.