Building the Pump System
-This section will teach you how to build a system to capture and pump Co2 into a 5L mini keg or a 2 liter bottle.
The finished system -> 
-So why must we build a pump, can't we just use a bicycle pump?
The problem with using a bicycle pump is the source of gas that the pump uses. A bicycle pump sucks in surrounding air from a non-controlled point, making it virtually impossible to feed the pump Co2 from a balloon. The pump that I designed only allows gas to enter the pump from one location (the check valve); this allows us to control the type of gas that gets pumped into the beer (Co2 from the capture balloon). If air (not Co2) was allowed to enter the pump and was then pumped into the beer, the oxygen in the air would cause the beer to go stale (in addition to not carbonating the beer).
-To start, we need a way to pressurize a 5L mini keg. In order to do this, it is necessary to insert a valve into the re-useable bung plug. The valve is a presta valve (this is from a bicycle inner tube). The valve on a car tire, and most bike tires, is a schrader valve, the presta valve is much thinner, and has a lock-ring; that is why the presta valve is used. You must cut the valve out of the inner tube, but keep some rubber from the inner tube on the valve to help the seal (cut this small enough so that the rubber end of the valve can fit through the inside of the bung plug).
-Slide a #36 O ring (or any other O ring that will seal this) down the shaft of the presta valve. This will make the seal so the system can maintain pressure.
-Drill a 1/4" hole in the center of the re-useable bung plug in order for the valve to fit through. Make sure to clean out any shavings or rough edges after drilling, to ensure a good seal. The O ring makes a nice seal along the inside of the bung plug. To further seal this, tighten the lock-ring just slightly tighter than finger tight (if you tighten the lock-ring too much it can crack the bung plug). At this point, the valve cap is just for looks, but later on it will be functional (after you drill a hole through it, and tie a piece of string through the hole... this will be explained later in the tutorial).
<--The O
ring is on the inside of the bung plug
-Insert the bung plug into the bung gasket and seat it on the 5L keg as you would normally. To seat the bung I usually use a piece of wood to press it into the keg (sometimes I have to tap on the piece of wood with a hammer if the bung is having a hard time seating).
This is what the bung looks like
seated in the keg. Notice the presta to schrader valve adaptor, this will enable
a pump hose to connect to it (Make sure that the presta valve is open, you
cannot see if the valve is open or closed once the adapter is on; if the valve
is not open it will be impossible to pressurize the keg).
-In order to tap the keg, it is necessary to remove the bung plug/valve assembly. Normally you would just push the bung plug into the beer, then recover it after the keg is empty. In this case, you must first purge the excess Co2 pressure from the keg (just like deflating a tire, depress the top center of the valve, the excess pressure will come out), remove the valve, then insert the tap (you don't want the valve sitting in the beer, it might produce off flavors, and ruin the valve). In order to remove the valve, you must first push it into the keg (after purging the excess pressure), remove the rubber grommet, retrieve the bung plug/valve assembly, re-insert the rubber grommet, then insert the tap.
-To retrieve the valve you must attach a string to it. To do this, drill a small hole through the top of the valve cap, then tie a piece of string to it (about 1 foot long); (clean) fishing line works great:
-Attach this valve cap to the valve on the keg
that you are tapping:
-Push the valve into the keg, do not push on the valve, but on the plastic plug. Try not to let the valve touch the beer if possible:
-Remove the rubber grommet, and pull out the bung
plug/valve (in this picture there is a different type of bung plug than the one
shown earlier, but this is done the same way for all types of re-useable bung
plugs):
-Seat the rubber grommet back onto the keg
without the bung plug/valve:
-Then, insert the tap.
-Now that we have a valve to allow us to pressurize the mini keg, we need a pump to pump in Co2, in order to force carbonate (and dispense in some cases)
-To learn how to build the pump, go to the next page:
