Blow-off Tubes or: How I Stopped Worrying and Learned to Love the Fermentation

A fair warning my dear readers; this article is either going to be a hit or miss for you. If you're intimately familiar with the benefits of creating a blow-off tube during primary fermentation and how to do so then you may want to skip ahead and check out our first Signature Series brew kit.


This article was inspired by two friends who have just begun their brewing adventures; one had his airlock pop off while the other asked me how he could prevent such a thing from happening to him. Before I go into the facts I have an humorous personal experience to share.
During my first summer as a brewer I decided to come home one weekend from my residence in New York to New Jersey to spend some time with my family. I had been planning a brew and I had some NJ buddies who wanted to see what the fuss was all about so I was happy to take some time from my weekend and brew at my mother's house with them. The recipe was a Chocolate Stout that I was very excited about.
The brewing went smooth; my friends were more interested in brewing and beer than ever, and overall it was great day. I had asked my mother where the coolest place in the house was, after all it was summer and I wanted to maintain a proper fermentation temperature. She let me know that her room was the coolest place in the house; naturally we can predict what happened next. Unfortunately for me (in the long run fortunately because I love this story) I was unable to predict the outcome and affixed a basic airlock to the carboy.
The next morning I was sound asleep in my bed located in NY. When I awoke around 4:00am to 4 missed calls from my mother you could imagine the fear and panic that ran through my head. I hurridly called her only to find myself on the receiving end of a very long string of words that I was not expecting to hear, especially from my mother! Turns out the carboy had exploded around 3:30am shooting a fountain of beer and krausen into the ceiling and promptly raining down upon her to awaken her. It should be mentioned that my mother is not a big beer drinker and when she saw the dark stout seeping into her white bed sheets it did nothing to lighten the situation.
Some valuable lessons were learned that day. One, it is very hard to scrub 10ft tall ceilings. Two, taking a day off from work to scrub for 5 hours takes all the fun out of taking a day off from work, and three, I would never do another fermenation without a blow-off tube again.

SetupBlow off tube equipment

Setting up a blow-off tube is incredibly easy, takes very little time, and will save you many future headaches. Blow-off tubes help to relieve the pressure created inside of your fermentation vessel by the CO2 generated.
You will need the following equipment:
- Fermenting Vessel + Bung if you're using a carboy
- Food grade tubing (we recommend 5/16")
- Container that can hold fluid
Note: In our pictured scenario I am using a gallon water jug as a fluid container. The knife pictured is to cut a small hole in the gallon jug to stick the tubing through.
Step 1: Sanitize - Be sure to sanitize your carboy bung and plastic tubing prior to creating the blow off tube. In addition use a small amount of sanitizer combined with water in your fluid container.
Step 2: Insert your sanitized tubing into the carboy bung. You will likely need to be a little forceful to get a secure, snug fit. Don't worry, this is how it should be. You want to make sure that your bung will leave no room for any potential contaminents to enter your fermenting wort.
Step 3: Affix your carboy bung to your carboy (or in the case of using a fermentation bucket just affix your tubing to the grommitted hole on your lid) and run the tubing into your fluid container. You will notice that in the example provided we keep the cap on and only put the tube through the small hole we cut to avoid anything potentially entering the sanitized solution.
These three easy steps will ensure that you avoid any messy clean ups during your future brews. During active fermentations you will often hear the sanitized solution bubbling; have no fear this is normal and a healthy sign of active fermentation.
If you have any other questions about creating a blow-off tube that we may not have covered feel free to email me personally at!