2.5 gallons in a 5.5 gallon bucket?

[Chaddyb]

Would this be ok or is there too much headspace?

 

[Golddiggie]

3 gallons of headspace, IMO, is a bit much. Unless you can purge it of air (using CO2) after you pitch the yeast. The most headspace I like to have in a fermenter (without purging with CO2) is one gallon. Even then, that's for for 4+ gallon batch sizes. If it's less than that, like 2.5 gallons, I prefer to use a 3 gallon fermenter.

 

[meschaefer]

IMO your fine. Quite regularly I ferment 3 gallon batches in 6.5 gallon carboys with no perceptible off flavors or staling noticed by experienced palates. If you think about it the extra headspace could be a benefit at the start of fermentation when we are going to great lengths to aerate or oxygenate the wort when we pitch. Once fermentation gets going any oxygen getting into the beer will be quickly used up by reproducing yeast or be flushed out by rising CO2.

 

[malevolent]

Did a split batch of stout, 3 gallons per 6.5 gallon fermenter. No issues. Nice and tasty

 

[Chaddyb]

I can see where it wouldn't really matter for primary, but I wouldn't want to bulk age something in a 5 gallon secondary.

 

[kh54s10]

IMO co2 is heavier than oxygen so no matter the headspace there will be a protective co2 layer atop your beer. The only way to have a problem is if you have a breeze strong enough to blow out the co2 layer.

I have done a couple of 3 gallon batches in a 5 gallon Better Bottle and a 5 gallon bucket. I'm drinking the first and it's fine. The second is in bottles.