Originally Posted by TheHumanSwing
So I am two weeks into fermenting a five gallon batch in a 6.5 gallon glass carboy, and today I noticed that my airlock started sucking in the starsan in it. Why is this happening?
Your beer sucks.
Because it's cold and that creates a vacuum in the fermenter because the volume of air decreases. And there's no CO2 pushing out on the airlock.
It's fine. I've spilled enough StarSan in a beer before to count it as a dry hop addition.