I've started making most of my beers 10 gallons at a time, since it's very little additional effort vs. making 5 gallons, and we have those lovely 15 gallon brew pots at the brewhouse. My only complaint has been splitting my batches into two carboys/buckets, because it means double the amount of cleaning/sanitizing (I know, I know, I'm lazy...). Plus, you know, bigger is better! So I have been looking for a relatively economical way to ferment 10 gallons in a single container. Some folks ferment in a sanke keg, and Morebeer sells some awesome looking Speidel plastic fermenters, but I don't have a sanke floating around, and the 15 gallon Speidel goes for $65 (it ships free though). Enter hbt (where I learned about it) and ebay (where I found it). It's a 13 gallon HDPE food-safe container with an airtight lid and handles for around $35 shipped. Punch a hole in the lid for an airlock/blow off, and you're all set.
With luck, I'll be able to test one of these before we have to pack up and move to our new brewhouse. I'll report back here with my results once I have fermented a batch.
-Adam
UPDATE: much success!
Just kegged the 10 gallons of stout that I fermented in my new 13 gallon fermenter. I got pretty close to 11 gallons into the fermenter, and it blew off fairly agressively (you definitely need a blow off for 10 gallons of a big-ish beer). I filled both kegs completely full, so I got slightly more than 10 gallons of finished beer. Cleanup was a little tricky, as there was some serious krausen on the inside of the fermenter. A few minutes on the carboy cleaner with some hot PBW softened the stuff up and I was able to finish the job with a bit of work with a sponge.
Other than the fact that moving 10 gallons of beer around is a lot of work, I'm sold. I'll be using these fermenters every time I make a big batch.
-Adam