What size keg to get for 23L brews?

Question

I'm thinking about investing in a keg, etc. done some reading but still have a lot of questions. I currently bottle from brew cans which fill the fermenter to 23L and comes out to about 30x 750ml bottles (22.5L).

I have seen many different size kegs. Does it matter the size? Do you need to leave space in the keg for gas/air or is this bad?

For example I saw a 30L keg for sale 2nd hand. Could I brew 22.5L in this 30L keg?

Also saw 18L kegs - if I got two of these kegs could I fill each with 11L? If I got one could I fill it to the brim (18L) and bottle the remaining few litres?

Answer 1

The ideal keg size for a 23l batch is 23l or as close as you can get above that.

You can use a larger capacity keg with no problems, but you will end up using more CO2, since you have to pressurize a larger volume.

Using smaller kegs is also possible, but a bit of a pain since you have twice the work to do cleaning, sanitizing and filling, and again, the one half-filled keg represents a waste of of CO2.

Corny kegs are popular with homebrewers, which hold 19 liters. I used to brew UK gallon sizes (23l) but switched to the typical 5 US gallon batch (19L) when I moved over to corny kegs. Since you'll have about 3 liters left over from your usual batch, you could fill two 1.5l PET soda bottles first, with a little priming sugar, and then fill the keg afterwards. This will avoid wasting any beer from the batch or using more CO2 than you need, while also giving you a couple of bottles over, which can be handy to give to a friends, take to parties etc.

Do you have place to keep the kegs chilled, and hooked up to CO2? Kegs are certainly a lot easier than bottling, but they do require the right environment (temperature and CO2 pressure) to provide a good pour.