The Beginners Guide to Blow Off Tubes

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First off, I want to personally thank you for visiting and sticking around! Second, before reading this, please have an Ice Cold Homebrew or equivalent Craft Brew. No Coors allowed!
Now that the Intro is out of the way I found it necessary to submit this article for those looking for answers. A no BS approach so you dont have to siphon through countless threads of the "OH NO! MY KRAUSEN IS PIPING THROUGH MY AIRLOCK!"
Whether you are an experienced Home brewer or Beginner we ALWAYS have questions and worries. Simple or complex somebody has multiple ways of answering and rectifying any situation.
Lets Begin shall we?
So you finished brew day with a wonderful homebrewed wort in the carboy, bucket, etc. fitted with a airlock. You pitch your chosen yeast strain into your fermenter after proper aeration and let her sit. Now we can get into proper fermentation temperatures and the effects of such but that will be for another article! So now the waiting begins and you let the yeast do what comes natural to them, eat sugar and poop out booze!
Now if you are like me, you can't help but stare at your creation multiple times a day. You notice all the changes occurring to your now early fermented wort. It may have a nice little layer up top of some ugly looking foam, this foam is called "Krausen." If you have the day off you can actually watch it grow in the beginning stages of fermentation which happen to be the most vigorous! One BIG problem can occur during this stage of fermentation with a vessel not fitted with a blow off tube OR has enough head space where such a high krausen is formed it blows through your airlock! YOWZAH! The Key is to not allow this to happen.
Back to our day of viewing the krausen rise, if you have ANY feeling of it not blowing through your airlock then by all means sit back and relax. If you are like me, I HATE waking up to a gnarly mess and possibly infected beer due to my lack of putting on a blow off tube. Now the obvious thing to do here is simply affix a tube Right after pitching the yeast set it and forget it. But in a pinch where the krausen is just to high for your liking below I will show you how to handle it!
1. No Rinse sanitizer - Recommended
2. 3 Piece Airlock
3.5/8" OD / 1/2" ID silicone tubing - Lowes or Home Depot for ~$.48/foot
4. Bucket, Bottle, something to hold your sanitation solution

5. Water Filter and Or Bottled Water

6. Large Office Clip - Optional

7. Spray Bottle with Star San solution or No rinse substitute
Lets go!!!!
Now I brewed a Golden Ale. OG at 1.048, a little beer in my eyes, I did not think of using a blow off tube. Carboys are placed in my ferm Chamber Ambient Temp @ 15.5C and wort temp 16.2C. Take A look at the krausen 12 hours after pitching

Quite High for my liking. Now I never thought I would need a blowoff on this little Ale, nor do I like to question it so I ran out to Lowes and got the tubing 5/8" OD - 1/2" ID! Upon returning Home I noticed it had climbed again, very close to the top of my carboy. Not good! Now next are the few steps you need to do once you have everything on hand!
Step 1 - Connect your water Filter to the appropriate faucet or hose and fill up your bucket or bottle and add your no rinse sanitizer accordingly
Step 2 - Measure by eye or by measuring tape your blow off tube length. This is not a science at all, just don't cut it to short! You can't add material!
Step 3 - Place your Bucket/Bottle of sanitizing solution near your carboy at the correct length for your blowoff tube.
Step 4 - Clean your tubing!!! Clean it well. You dont know what it came in contact with while on the shelves at the hardware store. Once clean sanitize it! I do so by spraying my hands down first, then spraying the outside and inside really good.I place my thumb over the hose ends and swish the hose back and forth for a minute or two.
Step 5 - Spray the entire top area of the carboy including the 3 piece valve, bung etc. You can never be to careful, especially with young wort! If you already have a disaster scenario with krausen everywhere DON'T WORRY! Simply start cleaning up just the airlock first! we must secure the tubing as soon as possible.
Step 6 - Spray the end of your blowoff tube inside and out once again.
Step 7 - Remove the top plastic cap and clear slider from airlock and quickly place your blow off tube end over the male end of the airlock. Im not going to lie, this will not be easy for some. You need to wiggle the crap out of the tube to get it to slide OVER the male end of the airlock.
Like this:

Step 8 - Place the other end of the now affixed airlock blow off tube into your bucket or bottle with star san solution. Now you can do this vice-versa which I would recommend but if using a smaller bucket it could be hard to keep the end of the hosing in while finagling with the tube to get to slide over the male end of the airlock.
Optional Step 9 - Using an office clip and affix the hose submerged below the surface of the star san solution in your bucket or bottle.
YOU ARE DONE! If you have an excessive blow off scenario you should use clean buckets with a sanitizer solution in a sort of rotation. Using a spare! Below is an image of the little Golden ale almost Blowing off

Yes this is lengthy, But needed for those with questions! I may have answered many with this or just one, but as long as it helps other homebrewers I am happy!
Thank you
A one inch piece of vinyl tubing goes right down inside the mouth of a glass carboy. That's what I use. Hooking the tubing up to the airlock seems maybe a bit less cumbersome. The one inch tubing is big bulky and not very flexible, but it's also never going to get clogged with goop.
Quite frankly I never thought about attaching the hose to the airlock. My initial inclination was to find hose that would fit in the bung hole. That's just too small be practical, therefore I went for the one inch tubing
I also cut off the "X" at the bottom of my 3-piece airlocks as well. This eliminates a spot where a clog could occur.
Might also want to saw the bottom of the air lock off. About 1/4in, it tapers down into a opening just small enough for hop bits to clog, and painting your ceiling green
I just shove cleaned and sanitized tubing into the bung itself, saves some height if size is at a premium.
The filtration of the blowoff water seems like overkill to me.
@Devinv Thanks for that! I hadn't taken a look at the bottom of my 3 piece units, I've painted my ceiling once. Wife was not happy....
This method works great. I have been doing this for a couple years now and have had plenty of blow off. Never had the tube get clogged. Cutting the bottom off though doesn't sound like a bad idea.
I don't bother filtering blow off water though.. not necessary. Not even sure the reasoning behind such a step. that water should go nowhere near your beer and it is sanitized water anyway with starsan in it.
The reason I do so is it begins to smell to high heaven. Also for those fermenting in a closet with bugs nearby, they smell it,right out and congregate towards it
Love the idea of the article, and it's great you've taken the time to write it up. I apologize that this may come across as negative, as I don't want to sound like I'm dumping all over this. But you did mention that this would be a 'no bs article'. So, to improve it, I would cut out the fluff and get straight down to brass tax. For example, cut out the multiple paragraphs in the intro where you're 'setting the scene' like a journalist, from "So you finished brew day..." all the way to "I will show you how to handle it". Replace it with 3-4 simple lines such as this, for example:
"Within the first few days of brewing, it's possible that the fermentation of your beer will push sticky gunk (called Krausen) up through your airlock, jam it, and cause half of your beer to explode all over the room. To avoid that, you need a blow off tube. Here's what you'll need to make one, and how to do it..."
Just my opinion.
I use a standard bung, and a short ~ 2 inch piece of copper pipe fits into this, then a length of tube...not sure the exact dimensions/ID/OD of the various pieces, but it's simple enough to piece together...
Nice article.
I have used a 1" tube right in the caarboy as someone else has stated. Works well but the tube is stiff.
Like the idea of the brass pipe, seems like that would be less likely to clog and it would then be just a matter of changing out the airlock with the other bung/pipe/tube.
Nice tips.
1/2" ID tube also fits perfectly (nice and snug) over the center nipple on a carboy cap. Thermowell goes down the other nipple.
A cautionary tale about using a blowoff tube: if you cold-condition after fermentation is complete (aka "cold-crashing"), switch out to an airlock. I managed to suck back 4 cups of starsan into two fermentors because I left the blowoff tubes in the jar of starsan when I dropped the temp from 68 to 35. I would have never thought that could happen.
I would also suggest to place the sanitizer and end of the hose below the beer level to avoid the possibility of the liquid being siphoned back into your beer after high Krausen.
I also use the 1/2" I.D. tubing and three-piece airlock. But since I ferment in a converted mini-fridge, I don't have room for a bucket. Instead, I use old whiskey or bomber bottles. I sanitize the bottles, but I don't add any liquid. If I have a particularly active fermentation, I keep an eye on the bottle and empty it once a day.
A word of advice, though: don't try to add tubing to an airlock while it's on the carboy. I tried that twice - once I broke the airlock; once I pushed the bung and airlock into the carboy. Now I slip the tubing onto the airlock tube first, then set a bung on a flat surface and shove the airlock into it.
And as someone else mentioned, I always replace the blow-off with a regular airlock setup before I cold crash; I don't want to suck anything back into the carboy.
Great intent but too much fluff as mentioned above. This ain't a novel!
Additionally if you are doing a beer that needs cold crashing, I switch to a one piece airlock as it's tougher to suck back on those or barely fill the 3 piece.
I dont' use carboys for my fermentations - still use the "ale pail" plastic buckets.
I went to my local homebrew store to get materials for a blow-off tube, and they told me I could just pull the rubber gasket off the lid, and shove the tubing through the hole. I put the other end into a gallon milk jug filled with sanitizer. Works great.
Had a broken airlock that I cut the bottom off, placed some tubing on one end, then put it into a rubber bung. seems to work good with my cider. When the foam dies down, replace it with a separate bung and airlock.
I have had the Starsan suck back into the fermenter with just a little decrease in temperature. A good reason to use the Starsan. Forgot to take off the blow off once when I started cold crashing. The Starsan was gross with blow off and gnats in it. Beer still turned out great. Only told the story after people said how good it was. LOL