Forced Carbonation of Kegs

Carbonating your beer keg can be done quickly and simply using the following forced carbonation procedure. After a little practice you should achieve correct carbonation in just a few minutes.

Fit a length of sterilised tubing to your fermenter/Blue Cube tap. Make sure this tubing is long enough to reach the bottom of the keg so that you fill the keg from the bottom without splashing the beer. You will notice there is a tube in the keg running from the top of the keg to the centre at the bottom. This is called the Dip Tube and is used to draw the beer from the keg. It is the "Out" or "Liquid" side. There is also another short tube - the CO2 inlet, where the CO2 is injected into the beer. Fill your keg should to approximately 12-25 mm from the bottom of the CO2 tube. Once the keg is full, replace the hatch cover and place the keg in your fridge. Connect your gasline from the keg to the gas bottle. Turn on the gas bottle, set the pressure on the regulator to between 70 and 100 kpa (10-15psi).

You need to purge the headspace of the keg of any oxygen to protect the beer from oxidisation. Release the pressure release valve on the top of the keg lid. This will allow the CO2 to flow into the keg and the air in the keg will flow out through this valve. This is called burping the keg and is best done in three short bursts.

After filling and purging the keg it is now ready to be carbonated. The following is a rapid force carbonation method which can be employed to carbonate a keg in a short period of time. It is very important that the beer is as cold as possible for this to work effectively. You may have to refrigerate your filled keg for a few hours to ensure the contents is as cold as your refrigerator can make it.

Lay your chilled keg on its side on the floor so that the gas inlet post is at the bottom. If you think of the keg as a clock face, you want the gas inlet at 6 o'clock and the liquid outlet at 12 o'clock.

Turn the gas bottle on and increase the pressure on the regulator up to 300kpa. Attach the gas connection to the gas post. At this point you will hear the gas going into the keg rather loudly. This is perfectly normal.

With the keg on its side and the gas inlet at 6 o'clock roll the keg back and forth fairly vigorously (imagine you are rolling pastry) for 50 to 70 seconds. The amount of time that you roll the keg will depend on the type of beer and the desired level of carbonation you want. As a general rule if you have a Stout, opt for a lower carbonation and roll for 50 seconds and if you had a pale Australian lager, roll for 70 seconds. These times are based on a full keg, if you had a half full keg reduce the rolling time by half.

When you have finished rolling the keg turn the tap on the gas bottle off. (Very important: Don't touch the regulator! Reducing the pressure on the regulator can result in beer going back up the gas line and into the regulator - this makes a real mess and may damage your regulator). Now continue to roll the keg back and forth. You will see the pressure on the regulator dropping as the gas is absorbed by the beer. Roll the keg until the pressure does not drop anymore. We are aiming to achieve a stable pressure between 140 and 180 kpa. The amount of pressure that you want in the keg will depend on the type of beer and the desired level of carbonation you want. As a general rule if you have a Stout, opt for a lower pressure e.g. 140-150 kpa and if you had a pale Australian lager 180 kpa.

If the pressures falls below the level you want then you simply turn the tap on the gas bottle back on and roll for another 10 seconds or so. Turn the bottle off and roll until the pressure is stable. Disconnect the gas. Put the keg in the fridge for 1 to 2 hours before drinking and release the excess pressure on the keg with the Pressure Relief Valve and pour beer normally. (remember to reduce the pressure on the regulator to pouring pressure before pouring - pouring a beer at 300kpa will not be pretty....)

If the stable pressure is too high and won't drop back to a level that you want, leave the keg out of the fridge for a couple of hours and release the excess pressure through the release valve. You may need to do this several times depending on the level of over-carbonation. Place the keg back in the fridge and when cold release the excess pressure again and pour normally. If the beer is still over-carbonated repeat this process.

If you are concerned about the risk of beer in the gas line and potential damage to your regulator, you can fit a non-return valve in the gas line which will prevent and chance of beer finding its way into your regulator. Its good insurance! Brewers Choice sells a easy to fit non-return valve specifically for this purpose.