Originally Posted by I_Brew_Drunk
I'v got a few 5 gallon carboys and a few 6.5 gal plastic buckets that I've fermented in. I prefer using carboys for primary but I don't like having to limit my batch size to 4 gallons. I know, I know, just ferment in the buckets right? I just really like being able to see my beer ferment and not having to worry about a tiny scratch botching my whole batch. Whats the max volume you would recommend for a 5 gallon carboy with a (3/8" I think) blowoff tube? I know I need to be careful and not over fill it because yeast could escape if the Krausen gets pushed out of the tube. Can I just over-pitch my yeast to compensate for that loss and just fill it pretty full?
Also, obviously under pitching yeast is an issue, but is over pitching a problem? Would that lead to greater risk of autolysis or some other yeast related problem or would the yeast just sink to the trub when the wort is out of dissolved sugars?
Different yeasts will give different amounts of kraeusen, so get to know your yeast.
Answers to your questions:
1) Recommend getting a 6.5 gallon carboy or Better bottle and doing primary in that.
2) Buy FermCap, fill to 4.5 gallons, and use a blow-off. With fermCap you will probably be fine most of the time, but occasionally you get a yeast (usually Belgians) that haven;t been told what FermCap does, and they go crazy anyway.
You can still make 5 gallons in a 5 gallon fermenter, it's just more effort. You need to hold back about 20 gravity points of sugar (half pound of fermentables). Start with 4.5 gallons, and when kraeusen is past, either rack to secondary and add the rest of the fermentables in half gallon of boiled water, or add straight to the primary. If you do this in secondary, the added fermentables will create CO2 in the fermenter and help protect the beer.
3) I think the 8 gallon suggestion beats all.