Setup for blow off and preventing sanitizer in beer

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Active Member
Jun 2, 2022
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Orange County, CA
I've really been struggling with this lately. I changed my homebrew set up to go from a standard airlock to a blow off tube into a bottle of sanitzer a while back. The first time I did it, I noticed overnight that my bottle of sanitizer had gone down quite a bit. I found out that the changes in pressure cause sanitizer to go back through the tube into your beer. After researching this quite a bit I'm nowhere. Apparently from what I've read the same is true with any airlock. I've tried rigging up things like balloons filled with co2 to prevent this to no avail. How do people deal with this?
Where is your blow-off jar located? If it is above the level of the beer in the fermenter, you can start a siphon with pressure/temperature changes, and pull in way more sanitizer than just by suck-back alone. So, make sure your blow-off jar is below the level of beer in the fermenter.

Another thing you can do is increase the diameter of the tubing going to the blow-off jar. Doubling the ID of the tubing increases the volume of liquid, that can be sucked into the tubing before any gets back into the fermenter, by a factor of four.

But, the most robust solution is to use something like the "Krausen Catcher:"


Edit: I got beat to the punch by @fluketamer :(

Brew on :mug:
You just accept that the tiny amount of air that ever gets in isn't going to be enough to ruin your beer before it's been consumed. For things highly dry hopped, it might be more of a issue.

As for your airlock, if it's filled properly, it won't suck back the liquid. It'll burp air through first. But only a tiny amount to somewhat equalize pressure on both sides.

When I use blow off tubes, likewise I don't put them low enough below the surface of the liquid in the bubbler jar for them to suck back that liquid to the FV. If you are not certain how deep that is then you can experiment prior to putting wort in your FV.

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