Blow-off tube vs. appropriately sized fermenter

So, I've wondered for a long time why some people preach that you should always, always, always use a blow-off tube. I think I've realized that they, for whatever reason, just don't use a big enough fermenter that allows the necessary head space for the krausen.

Obviously, there are exceptions to this. There is the occasional case of a beer fermenting wildly and over-flowing a fermenter which had previously provided adequate head space. Probably those cases can be blamed on some combination of over-pitching yeast, high fermenting temperatures, or some other mistake made by the brewer.

But why do people try to ferment a 5 gallon batch in a 5 gallon carboy? That doesn't make any sense to me. I mean, I know that when you have exactly 5 gallons in one of those, there is still a little bit of space left. But not nearly enough that I'd feel comfortable pitching yeast with it being that full.

I can't imagine that it is a matter of wanting to save space by using smaller fermenters, because that means you need something to catch whatever is coming out of the blow-off tube. So, you have an only slightly smaller fermenter, but an entirely separate container of some sort right next to it. Doesn't add up to saved space.

And also, don't you end up losing some of the final volume of the batch if it goes out through the blow-off tube? So, really, you end up wasting space where you could possibly fit another fermenter AND you end up wasting beer by inviting it graciously to go for a swim in some sanitizer.

I'm not aware of any beginner's equipment kit that comes with only 5 gallon fermenters. Except for small batch kits (Mr. Beer - 3 gallons? Brooklyn Brew Shop and other 1 gallon kits), they all come with at least one 6.5 gallon bucket/carboy, and then maybe a 5 gallon carboy to use as a secondary. So, it isn't a matter of newbies being led astray by the equipment they are introduced to as they begin the hobby.



Is there something I'm missing?

I think you may be jumping to conclusions here. My guess is most brewers preaching use of a blow off tube are using 6 gallon fermenting vessels. I've had plenty of blown off bubblers on 6 gallon carboys when pitching a calculated amount of yeast under temperature controlled environment. I doubt it is a regular practice to primary ferment in 5 gallon carboys by most home brewers.

I personally think that you have answered your own question(s). It could also be that "they" are also concerned about the possibility of infections in fermenters that have a lot of head space. I like the head space, that way I can harvest some of the yeast for later. The more money I save the more beer I can brew. It works well for me.

Cheers
Kev

geoffey said:

I think you may be jumping to conclusions here. My guess is most brewers preaching use of a blow off tube are using 6 gallon fermenting vessels. I've had plenty of blown off bubblers on 6 gallon carboys when pitching a calculated amount of yeast under temperature controlled environment. I doubt it is a regular practice to primary ferment in 5 gallon carboys by most home brewers.

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It may not be a regular practice, but I sure see a lot of pictures on this forum of 5 gallon carboys with blow-off tubes.

kev said:

I personally think that you have answered your own question(s). It could also be that "they" are also concerned about the possibility of infections in fermenters that have a lot of head space. I like the head space, that way I can harvest some of the yeast for later. The more money I save the more beer I can brew. It works well for me.

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Does the extra head space really contribute that much risk of infection?

I guess this is a hobby for which many of us do what we can with what we have. I just don't understand why the fermenter size is generally left out of the conversation when people start preaching about using blow-off tubes.

I use a blow off tube when I have a beer that is over 1.080 and I'm pitching a yeast that I have double stepped on the stir plate, even with the cooler set to the mid 60's I'm going to have krausen by the gallons.

Ive recently had two batches (both 5.5 gallons in my 7 gallon fermenter) fully utilize the blowoff tue. Insane!

When I read these threads about needing a blowoff I wonder.. I've made some reasonably big beers of the 5G size and I use a Speidel 20L (5.3G) fermenter.. there is not a ton of headspace.. but, either I'm lucky.. or possibly it might be that I control my fermentation environment to 65* with a water bath.

I'm going to try to build a thermowell out of SS tubing to get a better picture of my actual fermentation temperature.. but, I'd think that controlling the temp has a lot to do with it. I'll be brewing a 2x IPA soon and I will be adding a blowoff tube.. just in case.. but, I doubt I'll need it.

Blow-off tube preacher here. I use regular 6.5 gallon ale pales, and still start on a blow-off tube every single time and recommend others do too. It's not about using smaller fermenters. This is why:

signpost said:

Obviously, there are exceptions to this. There is the occasional case of a beer fermenting wildly and over-flowing a fermenter which had previously provided adequate head space. Probably those cases can be blamed on some combination of over-pitching yeast, high fermenting temperatures, or some other mistake made by the brewer.

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Yeast is a living thing. You can't say for 100% certainty that this batch will behave exactly like your last batch even with the same ingredients/process. I've had my blow-off tube actually get used (as in got blow-off) only a few times in ~40 batches, but using it every time saved me from cleaning up those few times. Some of those times may have been a mistake by me (I'm not perfect) or my equipment, who knows, but it's cheap insurance and has no real downsides.

I use a 6 gallon fermentor. I always use a blow-off. Why not? It's no trouble.

As far as infection possibility and headspace are concerned, it isn't a factor IMO. I've been brewing for over 17 years, and never once had an infection from all combinations of carboy and wort volume. It just isn't a factor.

I don't even bother with blow off tubes nowadays unless I'm using a 5 gallon carboy and a 5 gallon batch. I use Fermcap, so blow-offs and boil-overs are a distant memory. I like using 6 and 6.5 gallon carboys for my 5.3 gallon batches, and the extra head-space is a good thing. Sometimes I get a couple inches of Krausen, but it never threatens a blow-off.

I always use tight temperature control tuned to the specific yeast and whatever ester goals the recipe wants, 5.25 gallons in 6.5 gallon glass, pitch rate is always dialed in by YeastCalc, and always with 1" ID blowoffs into a large vessel of sanitized water. I have no desire to dump chemicals into my beer whether during the boil or during fermentation, so whether any krausen ends up down the proverbial tubes or not pretty much depends on the recipe. I don't do anything smaller than 60 points, and those rarely dump any krausen, but the big 100 point brews definitely will be huffing plenty of foam. It all gets captured without drama.

Besides, I love the "whomping" sounds emanating from my ferm fridge with the blowoffs in place. Much more impressive sounding than what a bubbler can manage. I have a double batch just finishing up that was highly entertaining this week

Cheers!

For what it's worth, the Heading of this thread is a pretty good example of a "false dichotomy".

If you're doing a big beer, fermenting it in a 6.5 gallon bucket/carboy, you can definitely run into issues of your airlock clogging with krausen, especially with some specific yeast strains. Cooler ferment temps definitely help, but as someone who as experience the extreme mess of an imperial stout explosion, I'd rather not risk it. It's no more difficult to use a blow-off than it is to use an airlock, so I don't see the point in not taking the extra precaution.

blow off and pour it back in when it settles....
Be clean

I know that I use a blowoff because I live in an apartment and can not risk an overflow in my unit. But I also do not see why it matters what setup someone uses if it is what they are comfortable with.

If the yeast is a beast, you may need a blow-off. 5 gallons wort in a 6.5 gallon fermenter does not guarantee anything. Not into fermcap, but people like it.

For me, it is just standard practice. Even when I fill my 6 gallon with 5, and I think I have plenty of room, I rather be safe than sorry.

After we had a blow up in the Fermentation laboratory (AKA Bathroom) we have used a blow off and aux containment vessel on everything. And with proper cleanliness just pour it back in when it is done. nearly zero loss. Good engineers minimize loss

reverendj1 said:

Blow-off tube preacher here. I use regular 6.5 gallon ale pales, and still start on a blow-off tube every single time and recommend others do too. It's not about using smaller fermenters. This is why:



Yeast is a living thing. You can't say for 100% certainty that this batch will behave exactly like your last batch even with the same ingredients/process. I've had my blow-off tube actually get used (as in got blow-off) only a few times in ~40 batches, but using it every time saved me from cleaning up those few times. Some of those times may have been a mistake by me (I'm not perfect) or my equipment, who knows, but it's cheap insurance and has no real downsides.

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+1 one, and also +1 on why not?

I use a 6.5 gallon, and with a blow off I don't have to worry about over filling it. And I could rest easy knowing that my ceiling has no chance of of getting yeast on it. Yes you do lose a tiny bit if it goes through the blowoff tube, but not enough to lose all the extra that you are able to add.

I think you're cherry picking advice. If you look for posts that are about blowoff tubes it might make you think everyone starts with one. Use a blowoff tube when needed. I never start with one but am prepared if one is needed.

KettleCorn said:

blow off and pour it back in when it settles....
Be clean

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Please do not do this...

Komocabo said:

Please do not do this...

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Correct, wth is he saying.

day_trippr said:

Besides, I love the "whomping" sounds emanating from my ferm fridge with the blowoffs in place. Much more impressive sounding than what a bubbler can manage. I have a double batch just finishing up that was highly entertaining this week

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That right there is the most convincing reason to use a blow-off tube that I've heard yet. Thank you, I hadn't considered that aspect. Somewhat related, I'm an avid air-lock sniffer. What size/shape blow-off container is best for retaining the aroma of the expelled foam?

Pilgarlic said:

For what it's worth, the Heading of this thread is a pretty good example of a "false dichotomy".

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Cool.

mrtwister said:

I know that I use a blowoff because I live in an apartment and can not risk an overflow in my unit. But I also do not see why it matters what setup someone uses if it is what they are comfortable with.

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It doesn't matter. I just get annoyed when people preach something like a blow-off tube as the only way to without providing their reasoning or the parameters that lead to their choice. How can I assess the validity of somebody's advice if I don't know anything about them or why they do things a certain way?

signpost said:

I just get annoyed when people preach something like a blow-off tube as the only way to without providing their reasoning or the parameters that lead to their choice. How can I assess the validity of somebody's advice if I don't know anything about them or why they do things a certain way?

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I'm amazed that you've had that experience on this site. I find almost everyone to be very helpful...especially if you follow up with a question. Also if you get so annoyed at these people, why not address them in the thread, not start a new thread complaining about those people. Also, based on your first post, you seemed to know a lot about why people say they use them. It seems someone told you their reasoning.

Well he is why


Yep that a 14.25 gal Demi John with 11 gal of stout. 3.25 gal of head space and look at the blow off container. That's after it filled the first blow off container and put 1 gal on my floor

milldoggy said:

Correct, wth is he saying.

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Probably best not to do this...
We have lab type equipment.. I forget most do not have this type of setup.
Must be a closed clean system to do this cleanly.

Never mind...

Blow it off and throw it out.
you'll only blow off about a beer or two.

Darkness said:

Well he is why
View attachment 152087

Yep that a 14.25 gal Demi John with 11 gal of stout. 3.25 gal of head space and look at the blow off container. That's after it filled the first blow off container and put 1 gal on my floor

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You should put the container lower than the demijohn. A temperature shift witha decrease in the fermentation pressure or something could cause the blow-off liquid to siphon back into the carboy.

As for me, I haven't used a blow-off in about 6 years. I use Fermcap in my boil and it seems to carry over well to the fermentor. Even in those rare cases, I use foil and ferment in easily cleanable spaces, so the krausen just pushes the foil off and droops down the sides of the carboy. I personally think that's much easier to clean than a blow-off tube.

I use this setup, makes cleaning easier

I WANT your ferm fridge. I always use a blowoff tube in my 6 gallon carboy and ale pail (had blowoffs on both). I don't like the idea of adding chemicals to my beer, especially just to control krausen, seems counterproductive.

There is something about the "bulb blub" of active fermentation that is just fascinating and fun. Especially when there is an obvious backup and you get one amazingly loud and furious bubble.

Oops. Double post

What's the best way to secure the blow off tube? Do you just stick it in a certain distance?

Just shove it in a bit, half in to inch

Just out of curiosity is there any disadvantage to using a blow-off tube compared to an airlock?

Trox said:

Just out of curiosity is there any disadvantage to using a blow-off tube compared to an airlock?

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If your fermentation is real active, it will push out the tube vs blow up

When Im using my 6 gallon carboy, ill stick the 1" tube directly in, about half inch past the neck. When I use my 7 gallon carboy, ill still use a bung and stick the 3/8" (might be 1/4") tube in the hole, again about half an inch or so, just enough that it wont move.

For anyone using a bb, drill a stopper with a 7/8 speed bore bit and a 1" fits snuggly. Use the hollow plastic stoppers, not the solid rubber ones.

I guess for me, I just follow the "better safe than sorry" mantra for my life. It's really no more difficult to set up a blow off than it is an air lock, so why not just do it? Chances are, I'm not going to get into a life threatening automobile accident on my 5 mile journey to work, but I still put on my seat belt, just in case.

I always use a blow-off tube. If I would happen to blow Krausen all over the basement and make the whole house smell like beer my OL is not going to be happy!

HopSong said:

When I read these threads about needing a blowoff I wonder.. I've made some reasonably big beers of the 5G size and I use a Speidel 20L (5.3G) fermenter.. there is not a ton of headspace.. but, either I'm lucky.. or possibly it might be that I control my fermentation environment to 65* with a water bath.

I'm going to try to build a thermowell out of SS tubing to get a better picture of my actual fermentation temperature.. but, I'd think that controlling the temp has a lot to do with it. I'll be brewing a 2x IPA soon and I will be adding a blowoff tube.. just in case.. but, I doubt I'll need it.

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For the Speidel 20L, I know it says 5.3 gallons, but how much total volume do you think it will hold. I can't quite fit the 30L in my ferm chamber, but if the 20L is around 6.5 gallons like my carboy I don't think it will be an issue for fermentation.