Can you use a 5 gallon carboy for a primary?

I have been using buckets the whole time, but I want to monitor the fermentation process. Do I have to buy a 6 gallon, or can I use on the 5 gallons that I already have?

What size batch are you brewing?

5 gallon extract batches

5 gallons of beer in a 5 gallon vessel is not a good idea. Your krausen will find a new home outside the vessel.

That is what I was thinking

You could cut your recipe down to 4.5gals and use a blow off. Still may be sketchy, but an option. I have a 5 gallon better bottle, but I only use if for secondary or an occasional 3 gallon batch.

I am just going to get a 6 gallon better bottle. Is there a 5 gallon fill line marked on it? How do you know when you are at 5 gallons on it?

Do you have a decent bathroom scale? You can weigh the bb empty, add your cooled wort, then fill with water till you get to the right weight. 5 gallons of water weighs 41.7 lbs (8.34 lbs/gal at 60F). You then have to multiply that by your OG to get the target weight. So for example, if you are brewing a beer that has OG=1.055, the target weight is (41.7 x 1.055)+(weight of the BB).

I just filled mine with exactly 5 gallons of water and marked the line with permanent marker. It’s plastic so it won’t come off. If it were glass you could use a sticker to mark it.

I’ve referred to this image in the past. The 5 gallon mark is roughly 1/2way up the top frosted ring.

This is one of the most foolish things in the industry (has to do with wine, legacy, history, yadayadayada).

You can’t ferment 5 gallons of beer in a 5 gallon carboy just like you can’t ferment 1 gallon of beer in a 1 gallon jug (without blowoff assemblies).

I know that 5 gallons carboys are designed to be 5.5 (maybe 6) but that’s not enough of a difference.

You want 5 gallons of beer, well how much are you fermenting? 5.5 gallons to account for loss. Are you using top cropping yeast, etc… etc… You then need a 7-9 gallon carboy at a minimum. If you don’t want to worry about blowoff assemblies.

There’s nothing wrong with using blowoff tubes, etc… but it’s kind of a hassle.

I just filled mine with exactly 5 gallons of water and marked the line with permanent marker. It’s plastic so it won’t come off. If it were glass you could use a sticker to mark it.[/quote]

Takes a bit of time but I mark all my glass carboys with electrical tape at every gallon for 1 - 5 gals as well as the 5.25 and 5.5 marks. I prefer the 6.5 gallon carboys over the 6 gal but I have a couple of both.

I just filled mine with exactly 5 gallons of water and marked the line with permanent marker. It’s plastic so it won’t come off. If it were glass you could use a sticker to mark it.[/quote]

Takes a bit of time but I mark all my glass carboys with electrical tape at every gallon for 1 - 5 gals as well as the 5.25 and 5.5 marks. I prefer the 6.5 gallon carboys over the 6 gal but I have a couple of both.[/quote]

Same here. I mark them at every gallon and then at 5.25, 5.5, 5.75, 6. I just use a sharpie. It fades with time, but I just fill it in again.

I calibrated my 6.5 gallon carboys and then posted this with the tape measure for others to reference.

I wouldn’t recommend it. This batch lost about a gallon, made a mess, and ruined a cardboard beer box. Live and learn.

Don’t feel bad. A few years ago I had this really high gravity stout fermenting in the bucket. I opened th closet door to check on it and it exploded. I was cleaning beer out of the that closet for a week. It still turned out good though.