How to Upgrade Your Blowoff System

The three-piece airlock features a very simple yet ingenious design. It was created as a one-way airflow system that allows CO2 to exit the fermentation vessel without allowing outside air to enter. It’s always done a more-than-satisfactory job at what it was designed to do but things have changed. You’re brewing more seriously now and the three-piece airlock is no longer suited for your needs.

Three Piece Airlock with a Floating Bubbler

Like many, you found this out the hard way. It all started when you realized the importance of yeast health and made the move to yeast starters. You did everything right, except what you weren’t prepared for was an extremely aggressive fermentation.

In fact, this was the most active fermentation you had ever witnessed. It wasn’t just CO2 gradually finding its way out of the fermenter. No, this was something different where the cradle within the airlock looked like it was about to explode.

Before you knew it kraeusen started to flow up into the airlock and because you didn’t want to risk contamination of your batch by removing the airlock you were left to sit back and watch it all unfold. The headspace within the fermenter simply did not provide enough room for the mass amount of kraeusen that was forming.

As the kraeusen worked its way out over the next day or so you noticed that it had not only completely filled the airlock but had also run out through the holes of the cap out onto the fermenter lid and even onto the floor. Then, you were left with a huge sticky mess that was rather difficult to clean up.

So, you reconsider your use of yeast starters altogether knowing that it may end up like this every time. Well, don’t do that because going back to life without a yeast starter is just plain silly. Instead, there’s a much better solution that happens to be very simple — changing your blowoff system.

How to Upgrade Your Blowoff System

All you need to do is get about 4 to 5 feet of food grade tubing much like the tubing that comes with your rack and fill kit and/or auto-siphon, as well as a bucket. This tubing will replace the airlock so the size of tubing that you get will be dependent upon the type of lid you have on your fermenter and the size of the hole in it.

Measure the hole in either the lid or stopper (whichever you use) and select tubing with an O.D. that is just slightly greater than that of the hole. You want the tubing to fit as snugly into the hole as possible to create a tight seal that will prevent outside air from entering.

After you’ve moved the beer to the primary fermenter you’ll want to sanitize the tubing and insert it into the hole in the lid or stopper. You do not have to worry about inserting the tubing very far into the fermenter and you certainly do not want to submerge the end of the tube. Then, fill the bucket about halfway with sanitizing solution and place the other end of the tubing into the bucket. And there you have your brand new and improved blowoff setup.

This may seem like it’s almost too simple but it is very effective. In fact, this is the blowoff method used by many larger scale brewers. It is just as effective as an airlock when it comes to keeping outside air and contaminants from entering the fermenter but provides an even higher flow channel that is necessary for more active fermentations where greater volumes of CO2 and kraeusen come about and need to be expelled.

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Jeff Flowers

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Jeff Flowers has been a self-described beer geek for over a decade now. When he's not chasing his daughter around, you can usually find him drinking a fresh brew and wasting too much of his time on both Google+ & Twitter.


  1. Thomas Berrich says

    New to using a kegerator. What psi should I use on my home brew Czech pilsner. As of now it’s on 11 psi for four days now. Tried yesterday and it’s a little flat still. Any info would be greatly appreciated.

    • Kemper says

      I let mine sit on 30psi for 1-day, then 20psi for 1-day, then 10 psi for 1-day. (Shaking the keg 2x a day to mix in the CO2 better.)

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