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How To Make A Soda Bottle Keg

by Robert Butler (rbutler@tiger.lsu.edu)

I. INTRODUCTION:

This document explains how to make a party keg out of a three liter soda bottle. This keg has the great advantage of being inexpensive to build, and very portable. A tap assembly is attached to the bottle while the beer conditions. Bottle pressure draws the beer when tapped.

II. CONSTRUCTING THE TAP:

First, drill a hole into the cap to accommodate the length of racking cane. Affix the length of cane into a hole in the bottle cap any way that is most practical for you. The prototype has the cane hot-glued into the hole. My working model uses a stopper to hold the cane in place. A drilled #2 stopper (fits most beer bottles) is inserted upside down into the cap, so that the narrow end points up when the cap is attached. This prevents the possibility of bottle pressure blowing out the stopper.

Attach a siphon cap to the inserted end of the racking cane, and a length of 3/8 i.d. Vinyl tubing (standard size) to the free end. Place a hose clamp on the Vinyl tubing. The siphon cap will help keep yeast sediment from being drawn when the bottle is tapped. The hose clamp seals the bottle.


      Hose clamp
      Tubing     \
             \    \
               C===X=====)
   Cap with    ||       ||
   hole----> _|HH|_     ||
            /  ||  \    ||
   Racking /   ||   \   ||
   cane----|-> ||   |   ||
           |   ||   |   ||
   Soda    |   ||   |   ||
   bottle->|   ||   |   ||
           |   ||   |   ||
           |   ||   |   ||
   Siphon  |   ||   |   ||
   cap ----|-> ++   |   ||
            \/\/\/\/    ||
                        ||
   Tube end lower       ||
   than cane end------> ||

III. NOTE ON SEALING

If you are using relatively un-molested tubing, you shouldn't need worry about the seal. If you are concerned, you can seal any potential source of leak (tubing to cane connection, or cane/stopper to cap) with rubber cement, hot glue, tape, plastic wrap, whatever.. One hose clamp works fine on my set up, but I make sure it's clamped down as far as it will go. You will know if your seal is compromised if you see beer sneaking up through the tube.

IV. PRIMING

Normal priming rate for bottles: 3/4 cup corn sugar, or 1 1/4 cup DME per 5 gal.

V. TAPPING

Just open the clamps and the beer will be forced out by the bottle pressure. When the pressure drops below dispensing level, just un-screw the cap to let enough air in and the beer will siphon out. That's why it is advisable to use a length of tubing long enough (18" or so) to allow for siphoning.

VI. COST AND COMMENTS

The cost of the soda bottle is free if you already purchase soda, or if you have friends who do. Alternatively, you could raid your neighbor's recycling bin. The other four required parts cost pretty much the same no matter where you shop. Chances are you probably have a pile of this stuff lying around. A quick glance at one of my catalogs shows a total of $4.00 for the tap set up.


      30" of racking tube (enough for two taps) - $2.00  
       1  Siphon tip - $0.50
       2" of Vinyl tubing - $0.50
       1  hose clamp $1.00

I have two of these plus the prototype, which I still use. I don't bother to adjust my priming sugar, as I desire good pressure for tapping. These bottles will indeed hold it, though they'll become hard as rock. I use these like mini kegs being tapped with an air hand pump, i.e. the beer will be consumed within a day or two -- or better yet, a party...! Since the taps are a part of the keg, you can tap any keg, any time.

Comments and suggestions...?
rbutler@tiger.lsu.edu
www.sound.net/~rbutler