I'm in the primary fermentation of mead, using one of these "big mouth bubbler" 5 gallon fermenters and an S airlock.

Initially, when the fermentation was really vigorous, the airlock behaved as expected, bubbles pushed through every second or so, and then slowed down. Recently, however, the level in the airlock is almost even - it's still slightly lower on the fermenter side, suggesting that there's pressure being held inside, but not much, and it's not going down. This despite the fact that bubbles are still clearly rising inside the liquid in the fermenter.

At one point, I took apart the lid, stopper and airlock, cleaned everything and re-attached it (thinking there might be some gunk preventing a seal), and this seemed to solve the problem for about a day (airlock immediately pressurized, and started bubbling every couple of seconds), but the next day, the problem returned.

Is there any explanation other than a potential leak somewhere? The fermenter is brand new.

  • 1
    You might see the answer to this question: homebrew.stackexchange.com/questions/12859/… . It's specifically related to the glass version but it mentions the issues you encounter with the plastic version, as well as the fact that Northern Brewer is curating the negative reviews.
    – AHigh
    Feb 4, 2015 at 20:39
  • Well, crap. I guess it's time to pay a negative review and hope to get a refund.
    – kevbonham
    Feb 4, 2015 at 23:11
  • Unrelated to the type of fermenter, my first and second batch I never saw bubbles in the airlock, nor ever when using the same bucket. I figure it just doesn't seal well... but the brew turned out fine every time
    – CDspace
    Feb 6, 2015 at 6:24
  • @CDspace - that's good to know. My hope is that because I saw some pressure, oxygen was still excluded. My main concern is that this is a wild ferment, so there's likely plenty of acetobacter present. If you sanitized everything, even if oxygen did get in it would probably just let your yeast do a little more aerobic metabolism, rather then promote vinegar formation.
    – kevbonham
    Feb 6, 2015 at 12:30
  • Airlock activity is not always a good indicator. How long has it been in primary? What is the current gravity? When in doubt, a good SG reading will let you know what's going on with your mead.
    – valverij
    Feb 18, 2015 at 13:51

2 Answers 2


It is normal for the air lock to slow way down after a couple days. It may bubble only once every few minutes. (And a watched pot never boils!) However, you may also have a bad seal. You can use the soapy water trick - mix a drop of dish soap in a glass of water. Then dab the water around the edge of seal and look for bubbles.


I have experienced the same issue when fermenting. I believe the problem is the lack of oxygen. Try an aeration stone or some other type of aeration. Your airlock should start to bubble once again. Jimbowilly

  • Adding oxygen late in fermentation would damage the beer.
    – Pepi
    Aug 24, 2015 at 17:30

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