What are the drawbacks (if any) of using a 4-gallon batch with a 5-gallon kegging system? And what if the batch is only two gallons?

1 Answer 1


Go for it. There's no harm as long as you purge the keg of it's air, replacing it with CO2. At some point, every keg of beer has only two gallons in it. Whether it's right at the start or if it's after 3 gallons have been consumed makes no difference. If you don't purge the keg of air though, your beer will become oxidized.

To purge, prior to racking your beer into the keg, hook up the gas-in line set to about 3psi and open the bleeder valve. Let it run for about 30 seconds. Then depressurize, remove the lid, and rack your beer into it. After you put the lid back on, pressurize to your desired psi to meet your volumes of CO2 target, bleed off the gas, pressurize, bleed, etc. for four bleed-offs.

  • 1
    I do it often. I guess the only minor downside to using an oversized keg is that you end up using a little more CO2 compared to if you used the right size. But it's not much extra CO2, and not worth worrying about.
    – mdma
    Apr 15, 2012 at 22:02
  • If you are habitually running into this problem, you could invest in a tap-a-draft or find a miller home draft (if they are still selling them in your area) and pour out the 'beer'. These are ^ ^π six liter bottles/kegs that last as long as a 'real' keg.
    – Dale
    Apr 17, 2012 at 19:12

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