Cleaning, Filling and Carbonating Post Mix (Corny) Kegs

There are almost as many techniques for kegging as there are brewers. Below is one that we have been using for may years. 

Some people like to force carbonate at higher pressures – up to 300 Kpa, some people like to carbonate into the headspace directly through the gas disconnect and post keeping it connected for some days, some people like to fill directly through the liquid post. 

Some people like to use PSI – in the 21st century!

All of these techniques have their proponents and detractors but we’ve found this one to be simple and to have stood the test of time.

1    Sterilise your clean keg by filling it with the same type of sterilising solution you use to sterilise your fermenter.  We use and recommend Oxyclean for cleaning and Star San or Stellarsan for sterilizing.  Into this place the tubing you will be using to fill the keg.  Replace the lid and allow the keg to sit for 20 to 30 minutes.  

2    Drain the keg well.

3    Purge the keg of its air by sealing the lid and connecting the gas line from the gas cylinder, to the gas inlet on the keg.  Turn the gas bottle on and set the pressure to 100 kPa (15Psi).  Allow the gas to flow for 30 seconds and then vent the keg by opening the safety valve to release all the pressure.  Do this three times, to ensure that all the air is removed from the keg before filling.  This is done to reduce the risk of the beer becoming oxidised.

4    Release all the pressure via the valve and open the lid of the keg.  Don't be worried that the gas will escape as enough will remain due to it being heavier than air.

5    Fill the keg from your fermenter using the food grade tubing, taking care not to splash the beer, as this may also cause oxidation.  Fill to within 50 - 75mm of the top of the keg.  Replace the lid on the keg. 

6    Connect the gas line to the gas valve on the keg and blow out any remaining air that still may be in the keg.  Do this by venting the air/gas through the safety valve as you did when you purged the keg in Step 4.  Close the safety valve and pressurize the keg to 100kpa.

7    Chill your keg in the fridge to 2 to 4 degrees Celsius.  This will normally take overnight.  The reason the keg is chilled is to allow the gas that is to be added to the beer to be more easily dissolved.

8    Connect the black liquid disconnect to the gas line from the bottle.  Turn on the gas and make sure the gauge is still set to 100 kPa.  Connect this disconnect to the liquid valve on the keg (the only valve that will take the liquid disconnect).  Leaving this connected, you can then dissolve the gas a lot faster by rocking the keg backwards and forwards.  This forces the gas to dissolve into the beer.  Rock the keg for a couple of minutes. 

9    Allow the keg to sit in the fridge for 12-24 hours and repeat this process.  This will allow plenty of time for the first lot of gas to dissolve into the beer.

10    Repeat Steps 8 and 9 over the course of three to four days.  Don't be concerned about over gassing the beer as the pressure set on the gauge will ensure this doesn't occur.

Dispensing The Beer

The easiest way to dispense the beer from the keg is to firstly turn on the gas and make sure the gauge is set to 100 Kpa.  Then connect the gas line, with a white gas disconnect attached, to the gas valve on the keg.  This is how the pubs dispense their draught beer.  This pressure will ensure a smooth easy pour and no carbonation will be lost.  It is extremely important to note that the beer line should be 4mm internal diameter and 2.4 meters long or 3.3 meters long with 5mm internal line.

Apart from smooth pouring and uniform carbonation this method also means no more adjusting your regulator as you will be both carbonating and pouring at the same pressure.