Head Space in Kegs?

[Ogilthorpe2]

Making the jump to kegging. I usually brew 2.5 gallon batches (in the fermenter) and usually end up bottling more like 2.25 gallons of clear beer. I bought a 2.5 gallon keg (Technically the keg (torpedo 2.5) says it holds 2.6 gallons), and I’m wondering how much head space is too much/not enough?

So my questions are these:

A) Should I increase my batch sizes slightly to make sure I get a full 2.5 in the keg, or is a little head space desirable?

B) Does the answer change depending on force carb vs keg conditioned?

 

[day_trippr]

I have a 2.5 and a 3 gallon keg. Look like short versions of my 5 gallon kegs, which if filled below the oem gas dip tube tip, leaves roughly a quart of tapered head space. I expect the same is true of the two short kegs: the capacity is dictated by the level where beer would reach the gas dip tube end. I should probably verify that some day, but those two kegs make up the glass rinser and drip tray catcher systems inside my keezer

Wrt force carbonation, all else equal the greater the surface area, the faster the beer will reach equilibrium. If you fill a corny above the top of the sidewall (which closely corresponds to the tip of an oem gas dip tube level) the head space surface area starts to contract, which will slow down force carbonation.

Otoh, keg conditioning using primer doesn't care that much about head space as the CO2 is created "inside" the beer.

Still, filling above the gas dip tube carries risk of blowing beer back up the gas line, so that's something that should be avoided. And to provide extra margin against that problem, one can cut the gas dip tube down to just long enough to secure its O-ring - I have cut all of my gas dip tubes down to between 1/2 and 3/8"...

Cheers!

 

[Ogilthorpe2]

Thanks for the quick reply.

So if my batch, after fermeter trub loss comes up a few inches below the gas dip tube, is the extra head space an issue? The surface area is the same as long as the level is below any tapering, but does it matter if I’m say 4-5 inches below the dip tube vs an inch below? Just trying to decide if I need to refine my batch size any.

 

[day_trippr]

I don't do keg conditioning, strictly "set and forget" forced carbonation using chart pressure. But regardless of carbonation method, if you are fermenting in a separate vessel, then racking to a keg for conditioning or forced carbonation, I think the best bet wrt quality is to have purged the keg prior to loading, do a closed transfer, then if conditioning, inject the primer as a solution using a plastic syringe through the stem of a bare gas QD plugged on the keg.

If you go that route, head space won't matter - at least in any deleterious manner...

Cheers!

 

[Ogilthorpe2]

I don't do keg conditioning, strictly "set and forget" forced carbonation using chart pressure. But regardless of carbonation method, if you are fermenting in a separate vessel, then racking to a keg for conditioning or forced carbonation, I think the best bet wrt quality is to have purged the keg prior to loading, do a closed transfer, then if conditioning, inject the primer as a solution using a plastic syringe through the stem of a bare gas QD plugged on the keg.

If you go that route, head space won't matter - at least in any deleterious manner...

Cheers!

Thanks.