Glass carboy for 5g batches do i need a 6.5g carboy?

Tomorrow i am planning on going to my LHBS and purchasing a glass carboy/air lock for a secondary fermenter. Since i will be leaving my batches of brew in a primary for 3-4 weeks i was looking to add a carboy so i can run two beer's at once. I was unsure though of what size of Carboy to look for if i am brewing a 5g batch. If i am brewing a 5g batch should i buy a 6.5g glass carboy? or a 5g? I know the less oxygen the better for fermentation but you also need room for the foam right?

By the way i wanted to say this forum has been extremely helpful and would like to give thanks to all the member's who have and who will help me out in the future !!!!

from all the reading i've done, you want some head space for primary fermentation, requiring a 6 or 6.5g carboy

All I've learned says 6.5g glass carboy for primary fermenting and even secondary. But a 5-6g carboy should be sufficient for secondary as typically that's a calm stage.

6.5 carboy gives enough headspace for the krausen usually. Though now adays with the price of carboys you might be better off getting a 6 gallon better bottle or a 6-7 gallon bucket with grommeted lid

If you are buying "a second primary fermenter" where you are going to start and finish in the same container by leaving it there for 3-4 weeks, 6.5 gallon is good, and even that blows off sometimes.

A pail is cheaper, but I personally prefer glass as well. Given the cost differential, if I broke my big one at this point I'd certainly consider a pail at half the price, but I've had it for ~15 years and not broken it yet. Knock wood.

If you are buying "a secondary fermenter" (start in primary, move to secondary after a week or two) 5 gallons is fine.

I greatly prefer the 6 Gallon Better Bottle to a glass carboy but in any case I recommend 6 Gallon or better. You will lose some to trub some to blowoff and besides, with fermentation going on there is no oxygen in the carboy because it has been displaced with CO2. Headspace is only an issue in wine carboys that will be sitting for a year or more, and not even then really.

BTW, I regret both of my 5 gallon carboy purchases. It limits them to only secondaries

I would like to go to use the carboy as a "Secondary fermenter", but i have read so often than using a secondary fermenter increases your chances of contamination and that it was not necessary for most beers, but i am still unsure

ohill1981 said:

I would like to go to use the carboy as a "Secondary fermenter", but i have read so often than using a secondary fermenter increases your chances of contamination and that it was not necessary for most beers, but i am still unsure

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i use a 5g carboy for a secondary. not a lot of fermentation happens in there.
i use it to clarify. a lot of people don't use a secondary at all.

I the Complete Joy of Homebrewing, Uncle Charlie uses a 5 gallon carboy, but attaches a blow-off tube until the krausen subsides. He then attaches the ferm lock.

BrewHerc

I use a 5 gal secondary and it works fine. If you time it correctly, there won't be a lot going on in the secondary.

I don't think you want a lot of headspace in the secondary (provided fermentation is basically complete) because the increased surface area can increase oxidation.

If you think you might want to use it as a primary one day, then you will definitely want the 6-6.5 gal.

All of my fermenters are 5 gal. I do use fermcap (anti foam agent) so I rarely have a blow off. If you don't mind losing some beer you can rig up a blow off tube. If 5 gal. is all that is available it will still work just fine, you'll just need to take other steps to make it work right.

Get the 6.5 gallon. Then you can use it as a primary and a secondary.
If you are trying to save a few dollars, then the 5 gallon will work fine.

i have 2 5 gal fermenters that i use.. .an i do my primary and secondary (if i do them) with no issues. I always use a blow off (and always will regardless of how big my carboy is). If i had to buy again and the cost difference was nominal, id buy a 6.5 gal but it is not a necessity at all.

If you can, get a carboy cap. They make racking much easier.

I'll also say +1 on the better bottle. I have a crappy back and the thing is so light, especially compared to a full glass carboy. No real worry about dropping it, etc. Ask to pick up both style carboys at your LHBS and then imagine ~5 gallons of beer in them and you'll see how heavy glass can be.

So you say you are going to leave your beer in primary for 4 weeks. They will come out nice and clear. So my advice is.....

Forget buying a 6.5 gallon glass carboy and spend the money on two fermentation buckets for the same price. Two fermentation vessels are BETTER than one.

dontman said:

BTW, I regret both of my 5 gallon carboy purchases. It limits them to only secondaries

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If they are sitting idle, try EdWort's Apfelwien recipe. It requires no headspace.