Fermenting in a 10 Gallon Corny Keg?

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JLeather

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Picked up a bunch of kegging stuff tonight from an estate sale (more on that later). Enough to get into kegging and start building a single-level brew station (couple March pumps, a few more kettles, etc). Among the items was (3) big corny kegs that I think are 10 gallon. I'm thinking I want to use these as fermenters. Anyone had experience doing the same thing? I figure I just need a spunding valve and a floating dip tube and away we go? Any issues with the excess headspace fermenting 5.5 gallons in a 10 gallon corny?

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5.5 - 6 gal of beer will typically create over 100 gal of CO2 (at atmospheric pressure) during primary fermentation. This will very effectively flush O2 out of the headspace. You are better off using an air lock for the first ~75% of the fermentation, and switching to a spunding valve after that. You get more volume of gas moving thru the headspace with the lower pressure provided by an air lock, and will end up with less residual O2 in the headspace.

Brew on :mug:
 
A spunding valve is only needed if you want to ferment under pressure. You could also just use a gas disconnect and put the other end of the tube in a jar of sanitizer. Floating dip isn't a requirement. You could cut a couple inches off the original dip tube or just open the lid and use an auto siphon.
 
@BBBF Hit the nail on the head. I ferment in two 5 gal corny kegs (9 gal batch total). I would just start with a gas disconnect with a line into sanitizer and cut a couple inches off the dip tube.
 
@BBBF Hit the nail on the head. I ferment in two 5 gal corny kegs (9 gal batch total). I would just start with a gas disconnect with a line into sanitizer and cut a couple inches off the dip tube.

I use spunding valves on my 10's & I bought a floating dip tube to try out, but I haven't decided if it makes more sense in the fermenter or my serving keg.

Another option that I forgot to mention above is daisy chaining your co2 post to the liquid post of another keg and using your fermentation co2 to purge the air out of the keg you will eventually be transferring your beer into. In this case, your spunding valve or gas disconnect will be on the empty keg.
 
I use spunding valves on my 10's & I bought a floating dip tube to try out, but I haven't decided if it makes more sense in the fermenter or my serving keg.

Another option that I forgot to mention above is daisy chaining your co2 post to the liquid post of another keg and using your fermentation co2 to purge the air out of the keg you will eventually be transferring your beer into. In this case, your spunding valve or gas disconnect will be on the empty keg.

This is what I recently started doing. I also have a floating dip tube in my fermenter (came with it). It is helpful in keeping a fair amount of trub out of the keg, but you do need to account for the loss if you want a full 5G in the keg. Last time I made a batch I wanted to find out just how much was left...I had 1.75 quarts remaining in the fermenter. I also put the same floating dip tubes in the kegs...so far so good.

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