I_Brew_Drunk

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I'v got a few 5 gallon carboys and a few 6.5 gal plastic buckets that I've fermented in. I prefer using carboys for primary but I don't like having to limit my batch size to 4 gallons. I know, I know, just ferment in the buckets right? I just really like being able to see my beer ferment and not having to worry about a tiny scratch botching my whole batch. Whats the max volume you would recommend for a 5 gallon carboy with a (3/8" I think) blowoff tube? I know I need to be careful and not over fill it because yeast could escape if the Krausen gets pushed out of the tube. Can I just over-pitch my yeast to compensate for that loss and just fill it pretty full?

Also, obviously under pitching yeast is an issue, but is over pitching a problem? Would that lead to greater risk of autolysis or some other yeast related problem or would the yeast just sink to the trub when the wort is out of dissolved sugars?

Thanks

BigRob

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You lose beer moreso than yeast when you fill them too full and they blowoff..
I filled my sanke right up the other day, and it's blown off a half gallon of beer before settling back down. Yeast loss doesn't seem to be an issue.

slarkin712

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Consider making a burton union type device that catches the blowoff and then returns it to the carboy. With this you can fill your carboy nearly to the top.

pgrebus

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BYO magazine has a DIY project for a Burton union. You might also try an anti-foaming agent.

inhousebrew

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I'd say four gallons to be safe. Or you know they do make 6 gallon glass carboys. A cheaper route would be the 6 gallon Better Bottles which are transparent plastic.
If you really want to push it I'd say 4.5 gallons with some anti-foaming agent and a cooler than usual temperature controlled fermentation.

I never worry about autolysis. Put it in the fermenter, take it out in a month and your good. From what I've read it is a risk at the commercial scale more so because 700 barrels of beer (or however much they make) sitting on a yeastcake creates a lot of pressure which causes yeast cells to burst. 5 gallons of homebrew isn't going to create that kind of pressure so unless you're leaving your beer on the yeastcake for a extended period of time you'll be good to go. As for overpitching, I don't think it's a major problem but if you can avoid it why not?

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duboman

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I fill my 6.5 buckets up to 6.25 gallons, I lose very little but always use a blow off tube. I generally hit by desired 6 gallon bottling volume every time!

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I_Brew_Drunk

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So with that ratio I could fill up to 4.81 and bottle around 4.6 gallons. might have to give that a try. So losing yeast through the blowoff isn't really as big of an issue as I thought?

Yooper

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No, I don't think so. He's using a bucket, which has a very wide headspace while the top of a carboy is narrow and so gives you less headspace. If you fill a 5 gallon carboy (which often holds 5.25 gallons- measure it to see) with 4.8 gallons, you'll have a huge mess and not so much beer. Losing the yeast isn't a huge concern- there are hundreds of billions of them in suspension- but you don't really want a big mess and to lose a gallon of beer.

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BigRob

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Make an 8 gallon batch and just fill 2 carboys to 4gal each

Calder

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Different yeasts will give different amounts of kraeusen, so get to know your yeast.

Answers to your questions:

1) Recommend getting a 6.5 gallon carboy or Better bottle and doing primary in that.

2) Buy FermCap, fill to 4.5 gallons, and use a blow-off. With fermCap you will probably be fine most of the time, but occasionally you get a yeast (usually Belgians) that haven;t been told what FermCap does, and they go crazy anyway.

You can still make 5 gallons in a 5 gallon fermenter, it's just more effort. You need to hold back about 20 gravity points of sugar (half pound of fermentables). Start with 4.5 gallons, and when kraeusen is past, either rack to secondary and add the rest of the fermentables in half gallon of boiled water, or add straight to the primary. If you do this in secondary, the added fermentables will create CO2 in the fermenter and help protect the beer.

3) I think the 8 gallon suggestion beats all.