I just acquired 2 5 gallon carboys from a friend. Can I use one as a primary or is it too small for primary. I know they are the perfect size for secondary.
Too small for primary.
you can use it as a primary, you will just lose a little to blowoff. Use a blowoff hose.
or you could make 4 or 4.5 gallon batches in it instead (multiply all the ingredients in 5 gallon recipes by .9)
I would not hesitate to use a five gallon carboy to ferment a batch of four gallons or less. IMO it’s best to ferment with a minimum headspace of one gallon to eliminate or reduce yeast loss due to blowoff.
I ferment 4 gallon batches in 5 gallon carboys. The only pain in the a$$ is when I dump the wort into the carboy, it builds up enough foam that it doesn’t all want to go in without it making a mess foaming out the top under the funnel. I’ve been contemplating going to 6 gallon carboys to alleviate that. I remember having the same problem when I brewed 5 gallon batches fermenting in 6.5 gallon carboys. Rather annoying.
I have one 6.5 gal & two 5 gal. I highly recommend going that route. You can have 2-3 batches staggered at a time. I still have blowoff in my 6.5 gal but I also shoot for 5.5-5.75 gal in my primary. That way I am bottling 5-5.25 gal after trub & transfer loss.
For over a year I was brewing ten gallon batches and wanted to temperature control the fermentation using a refrigerator.
I built a plywood frame for the five gallon carboys to sit upon. I drilled two wholes through the plywood and placed two 1 gallon milk jugs half full of water.
I then used PVC pipe as a blow off tube. Yes, I had blow off but was easily handled.
Yeah I’m thinking on buying a 6 1/2 gallon carboy at some point. I have 3 primary buckets right now also, and my bottling bucket. I am only 2 batches in and already am accumulating a bunch of stuff. My friend loaded me up over the weekend with stuff that has never been used.