Can you partially fill a keg & carb it properly?

So my father in-law and I are looking into brewing a five gallon batch of beer each and splitting it in half with each other. I currently keg and he bottles, so we were originally going to bottle the batch we each made and split that way. Well now my father in-law wants to start kegging after seeing how much quicker and easier it is than bottling. Plus his last couple of double IPAs or high IBU brews didn't carbonate too well in the bottles.

So with that being said I mentioned to him that if he does decide to keg, we could buy 2.5 gallon kegs to do this. Well originally I thought I would buy two of the 2.5 gallon kegs so I could keep one on tap and fill the other to loan him in the exchange (and vice versa). But then I was wondering, can I get away with buying just one 2.5 gallon keg instead of two? Fill the 2.5 gallon keg for him and then use one of my 5 gallon kegs for the other 2.5 gallons of brew. I'm assuming it will take more CO2 for it to properly carbonate 2.5 gallons of brew in a 5 gallon keg.

Does anyone have any experience with this? Are their any other drawbacks by doing this? Any thoughts, suggestions or input would be appreciated. Thanks in advance!

Yes, but it's a bit of a waste of CO2.

You will want to do more pressurize and vent cycles than you normally do in order to get the larger amount of O2 present in the headspace out of the keg. This is where the extra CO2 consumption will come from. It won't use any more CO2 per gallon in order to carb and serve than would a full keg.

Brew on

Fill the 5 gal keg, purge with CO2 like normal (alleviating the worry of getting all O2 from a half-full keg), carb like normal, push to 2.5 gal keg after carb (you would have used CO2 to empty the 5 gal keg anyway so the push to the 2.5 gal keg is not really 'extra'). Purge the 2.5 gal keg (this is the only 'extra' CO2).

I do this all the time when I take a 2.5 gal keg to events, just pull from one of the carbed cornys in my conditioning fridge.

jbrace1 said:

Fill the 5 gal keg, purge with CO2 like normal (alleviating the worry of getting all O2 from a half-full keg), carb like normal, push to 2.5 gal keg after carb (you would have used CO2 to empty the 5 gal keg anyway so the push to the 2.5 gal keg is not really 'extra'). Purge the 2.5 gal keg (this is the only 'extra' CO2).



I do this all the time when I take a 2.5 gal keg to events, just pull from one of the carbed cornys in my conditioning fridge.

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Great!! Thanks for the suggestion!!! The investment on two is quite a bit. So I was hoping there was a way to do this. Plus using a little extra CO2 in any method is better right now than to purchase two 2.5 gallon corny kegs. Ultimately I will have two on hand.

Thanks again everyone!!