I’d like to try fermenting under pressure but I only want to brew small batches (2 or 3 gallons). I have been looking at reasonably priced PET vessels that can be pressurized such as the various versions of the Fermzilla. I have read that it is not desirable to have a large amount of head space in the fermenter and the smallest pressure capable vessel I can find is in the 7 gallon range. Is it a problem to ferment only 3 gallons in a 7 gallon vessel under pressure. If so, does anyone know of smaller pressure capable fermentation vessel. Thanks.
A cornelius keg would work well, and they are readily available in 3 and 5 gallon sizes.
This might fit the bill.
I have a couple of these they work great for serving. No reason not to use them for your purposes
I use 5 gallon kegs as my fermenters for 3 gallon batches. I use them for both pressurized and non pressurized batches. They work great for me, especially now that I’ve started using a floating dip tube instead of the standard one. Aside from pressurized ferments, they also allow for spunding and closed transfers to your serving kegs.