2-2.5 Gallon Batch in 5 Gallon Corny Keg

[beerdrinker]

Hey,

Lately I have moved to brewing smaller batches, but brewing more often.

The one question I had is can I keg a 2 gallon batch without side effects? I figure that the kegs eventually get down to 5 gallons, so it shouldn't hurt to have an extra bit of headspace.

Or would it be best to invest in a 2.5 gallon keg?

Cheers,

Sean.

[ChrisKennedy]

That will work just the same as putting a full five gallons in provided you are doing a good job of purging the kegs prior to racking. Slower movement of CO2 into the keg is better.

[Docjowles]

That will work just the same as putting a full five gallons in provided you are doing a good job of purging the kegs prior to racking. Slower movement of CO2 into the keg is better.

Could you elaborate on why? Does the slow flow cause the O2 to gradually be pushed out instead of violently mixing and hanging around in the keg? I suppose that makes sense, never heard it before, though.

[The Leakin' Barrel]

If it's like purging the air out of a carboy for wine, since the CO2 is heavier than air, you put the CO2 in at a low flow rate to allow it to settle to the top of the wine (or beer) which will displace the air thus pushing it out the top. A high flow rate would obviously cause alot of turbulence. And since you will have a much taller headspace in the keg, a slower controlled flow rate is required.

You could probably accomplish this using the air inlet tube on the keg itself, but with that much headspace I would make up a standpipe with an elbow on the bottom. Sterilize it, hook it up to a bottle of CO2 then carefully lower it into the keg to near the surface of the beer, but don't let it touch the beer. Have a helper turn on and regulate the gas for you as you hold the tube. The elbow will allow the gas to flow out across the beer surface, displacing the air. You can check the progress of the air displacement with a match above the keg opening. If it stays lit, you're still pushing out oxygen. If it snuffs out, your headspace is full of CO2 and you're good to go. Install your keg lid in the opening and then charge your CO2 to the pressure you want.

[Rictanica]

I think you don't want to use to much flow due to the venturi affect. It will pull in oxygen from the outside, the same as if you had a leak in your supply hose.

[thatguy314]

Everyone talks about how CO2 is heavier than air, but not so much that it'll just always settle and form a nice blanket. There's plenty of CO2 mixed in with our air around us. If CO2 really just sat below air so well we wouldn' tbe able to crawl because we'd choke on the CO2.

You should let in slowly so it mixes with the air, then you vent it. Every time you do this, the air will be a smaller percentage of the total. Vent it a few times and it'll flush out the O2.

[beerdrinker]

The general idea I seem to be getting from this is that the extra headspace will make it harder to flush the oxygen out.

One idea that came to mind is that I may want to flush the oxygen out, and then naturally carbonate the keg to 'eat' the remaining oxygen. Do you guys think this may help deal with the oxygen issue?

Cheers,

Sean.

[Puttie00]

I've done it many times, just purge your tank a few time co2 is lighter then air you'll be just fine!!!