Minitap - Portable 2 liter keg

I found a nifty portable 2 liter keg that I tweaked slightly. Many thanks to Bill Bufkin who posted his instructions, and is quite possibly the beer gadget king of all time. My only modification was to use a stainless steel dip tube instead of flexible tubing. The advantage for me is the strength of the steel and the obvious advantages of stainless. I'm also leary of a compression fitting on a flexible medium, though it would appear Bill and others have had no issues.

Here are the parts I used:

• 1/4" brass tee
• 1/4" to 3/8" compression fitting
• 1/4" to 5/16" compression fitting
• 1/4" shrader valve
• Stainless tubing, I cut up a dip tube from a corny
• 1 washer with hole large enough to hold the 1/4" side of a compression fitting
• Standard hose gasket
• Beer tube
• Cobra tap
• 2 liter pop bottle
• Bicycle CO2 inflator
  

Here is the minitap assembly. From top to bottom the parts are: cobra tap, beer line, dip tube, 5/16" compression fitting, brass tee, Shrader valve (on side), 3/8" compression fitting, washer, gasket, 3/8" compression nut. Note that the dip tube is one piece, going into the top of the assembly and out the bottom.

The most important piece in the assembly is the 3/8" compression fitting. Notice that the diptube is smaller in diameter than the fitting. This allows the gas-in to flow down around the diptube and beer-out to flow up inside the diptube, all while sealed. To do this you need to drill out the inside of the 3/8" compression fitting so that there is enough room for gas to flow. Then to make a solid and secure connection between the cap and 3/8" compression fitting I soldered a brass washer on. This makes a really strong connection, but you could probably get away with some adhesive like J-Weld.
Drill a hole in your pop bottle cap and start the assembly. VERY IMPORTANT: Do not use the compression sleeve in the bottom fitting (you want the gas to flow around the dip tube and the sleeve would cut that off). Screw the compression nut down tightly inside the cap until the washer and gasket on the top of the cap are held firmly in place. Now screw in your Schrader valve, and pop on your CO2 inflator, connect your beer line with cobra tap, and you are in business.

Use
The minitap is easy to fill because it's basically a counter pressure filler. I take the cobra tap off and replace with a ball lock to my corny keg. Prime the empty bottle with a few pumps of CO2, then let the beer flow from your corny keg into the mini tap through the dip tube. I find that barely screwing the cap on for filling and unscrewing slightly to relieve pressure as needed will give a nice-quite pour that is foam free (just like a counter pressure filler).

When dispensing it rarely takes more than a shot or two of CO2 to give a good pour. Be careful and keep an eye on your minitap (it's easy for friends to get squeeze happy and over pressurize the bottle making foamy beer).