Long story short...I didn't have Vodka so had to use distilled water in the airlock. Life got in the way and over a week later I finally got back to the beer today. Fermentation has completed but the airlock contains a mixture of stagnant blowoff. A quick inspection and sniff test makes me think it's not contaminated, but the airlock is definitely sour-smelling from the stagnant blowoff. I've never not used Vodka or Star San and am wondering what the likelihood of a contaminated batch would be from an otherwise undisturbed airlock.

  • 1
    There is only a problem if the liquid is sucked in, and even then, the distilled water will likely not be contaminated. In any case, even Vodka could be pushed out by the blow off, and you will be left in the same situation...
    – Philippe
    Commented Jan 3, 2018 at 19:48

3 Answers 3


I think the likelihood of a batch getting contaminated this way is pretty low. Certainly be careful with cleaning and replacing the airlock. But generally speaking the airlock serves as a blocker for air exchange. If the airlock did become contaminated, the contaminants would still need to work their through the airlock and into the fermenter, which isn't super likely unless there was a large temperature or pressure difference. And even it if did there's a decent chance it wouldn't survive in the quantities that would get through.

To be on the safe side, I would check the gravity, clean the airlock, and give it a little longer. If when you're ready to package it there haven't been any large changes in appearance, gravity, or smell, you're probably good to go.


I stopped using vodka or sanitizer in the airlock 19 years and nearly 500 batches ago. No problem.


Only time will tell on this one, i use a little metabisulphite dissolved in water with a pinch of citric acid, in fact this is the same solution i use to sterilize everything. Take a quart of water add 1/2tsp meta and acid mix well you will smell the so2 gas coming out of the solution.

  • Just to point at the sulfide dioxide is toxic.
    – Lucas Kauffman
    Commented Dec 31, 2017 at 6:12
  • Even if this solution is not toxic, won't it ruin any bottle conditioning?
    – Robert
    Commented Jan 3, 2018 at 22:16

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