I'm brewing my first batch ever, and got a little worried that it wasn't bubbling after 24 hours as the instructions said it should. I've read a lot on here that says not to worry about a bubbling airlock, but I do have a question.

It does seem to be fermenting, it's been 2 days. I can see a krausen through the plastic. And today I noticed the airlock is indeed pressurized. The instructions called to fill the airlock about halfway. I missed the mark and filled it about three quarters.

Now here's the thing. I can clearly see there is pressure in the bucket. I can press on the lid, and see the airlock bubble. When I stop pressing on the lid, the airlock equalizes, then shortly shows pressure in the fermenter again. Yet I see no bubbling. Could this be due to the fact the airlock is filled too much? Has anyone else seen this kind of behaviour?

Lastly, thanks to all of the people on here, it's relieved many worries, with the simple DWHAHB.

EDIT It's a 5 gallon batch in a 6 gallon white plastic bucket. I put a flashlight on the lid, turned off the lights, and could distinctly see different light levels, dark at the 5 gallon mark, kinda chunky brown about an inch and a half above that, and empty above that. Three piece airlock.

EDIT2 Checked the gravity tonight, and found 1.007. So I think it's done. Perhaps I had a leak on the lid, perhaps I just didn't notice it fermented in the day I was at work. In either case, I've put it in the secondary fermenter (yes, I know it's not necessary, but I want to clear it up a bit). I smelled it, and it smells almost like Sierra Nevada Torpedo, tasted it, and I can clearly taste the hops flavor and bitterness. It seems it turned out okay. I'll check the gravity again on Sunday, and if unchanged, bottle it. FWIW original gravity was 1.058, but that could be off, it was hard to measure around the froth after transferring to the primary fermenter. Either way, I'm within 0.005 of the kits specs, so I think I'm good.

DOOD! I made Beer! Sorry, this is fun

  • Need more info on the fermenter. You say it's a bucket, but you also say you can see krausen. How is this possible? Buckets are not clear. Is it a bucket or clear plastic/glass carboy? Also how big is the fermenter and how big is your batch?
    – paul
    Dec 31, 2013 at 8:52
  • Also what kind of airlock - 3-piece or S-Shaped?
    – paul
    Dec 31, 2013 at 8:58
  • 3
    Your bucket is just leaking C02 somewhere. Its actually nothing to really worry about, happens all the time. Perhaps take off the lid and re-attach it, you might see bubbling in the airlock after that.
    – GHP
    Dec 31, 2013 at 13:39

5 Answers 5


No, I don't think the fill level on an airlock is going to prevent bubbling. Short answer, but I don't think there is more to it.

Edit: I found time to respond in more detail. I experienced the same thing (no bubbling, but pressing on lid squeezes out bubbles) in two-gallon bucket fermenters, so I looked carefully at the airlocks to see if over- or under-filling was the problem. I am convinced that the pressure of newly-formed CO2 in an fermenter can easily push through an airlock, no matter the fill level. I am not a scientist, but my reasoning is because the pressure needed to push a bubble through the airlock is correlated to the height of the column of water, as I understand it. A 1/2-inch difference in water height in the 3-piece airlock is negligible (see table below). In fact, it is amazing to me how little pressure is necessary in the fermenter vessel to get the airlock bubbling. In your case, as others have suggested, the problem is likely that the pressure needed to leak out the bucket lid is even less than pushing through the airlock. I would be happy to be corrected if my math or science is wrong.

H20(inches) Atmospheres        PSI (lbs)

0.0          1.00000           14.6959488

1.0          1.00252           14.7329826

1.5          1.00378           14.7514995

2.0          1.00504           14.7700164

Edit 2: This is a little oversimplified, because the air pressure in the fermenter also has to float the middle piece of the three-piece airlock before CO2 bubbles can be released, and the pressure of that is a function of the weight of the middle piece and its buoyancy in water. So the "cracking pressures" listed in the above table are a low by a margin. However, overfilling the airlock is likely to decrease the pressure needed for a bubble because the middle piece will be more buoyant in deeper water.

  • And no need to worry about it if sign of fermentation are visible.
    – Denny Conn
    Dec 31, 2013 at 16:09
  • +1 +answer for the PSI calcs, check my edit for an update on my brew, and thanks
    – CDspace
    Jan 4, 2014 at 7:35

Assuming you are using a white plastic HDPE bucket, not a carboy, then I'm not sure how you saw the krausen. Assuming you opened the bucket lid to see the krausen then you would have released some of the CO2 in the headspace. For bubbling to occur, the headspace must be full of CO2. In general, opening the bucket lid before 48 hours is a bad idea, unless you have access to a CO2 tank and can add CO2 back into the headspace, because you're exposing the fermenting wort to air, which can lead to oxidization (or worse, infection). Having the airlock filled too much will not stop it from bubbling.

Also assuming you have a 3-piece airlock, it's possible (however unlikely) that the floating bell piece is stuck, but again, unlikely, and I've never seen this. It's very common for airlocks to show little to no visible bubbling, as you'll see in many other questions (seems like you know this from your question).

The only way to truly know if your beer is fermenting is to take gravity readings and compare them to the original gravity, but I don't do this until it has had 5-7 days to ferment (especially if you saw a krausen or bubbles in the wort).

Knowing the type of fermenter, type of airlock, original gravity, type of yeast, etc. would all be helpful in providing a more detailed answer.

I'm not a big proponent of answering questions with "RDWHAHB", but when it comes to fermentation, generally the more you worry and mess with it, the more problems you expose yourself to. This isn't always the case, and calculated risks/modifications can fix/improve things sometimes (e.g. adding more yeast, changing temperature, etc.).

  • The fact that pressing on the bucket lid sends bubbles through the airlock tells us that there is nothing malfuntioning with the airlock. Dec 31, 2013 at 15:59
  • "The only way to truly know if your beer is fermenting is to take gravity readings and compare them to the original gravity" - I beg to differ. There is another way. You can always go the tried and true route and drink the stuff. If it gives you a buzz its fermenting/fermented :-)
    – fthinker
    Jan 4, 2014 at 0:57
  • Depends on the ABV :)
    – paul
    Jan 4, 2014 at 6:41

When I used to ferment in the white buckets, it was not uncommon to see the airlock not doing anything -- yet the beer fermented out fine. The white buckets are not the best for getting an airtight seal and the CO2 just leaks out where the lid fits the bucket (rather than pushing up the bell in the airlock). That, or the little grommet in the hole on top isn't holding a seal.

If your SG is dropping, you should be fine -- the yeast is taking care of business.


Can't you smell the alcohol, I'm having the same problem. Using a five gallon bucket with 2 gallons of mash. I can here it bubbling, and smell the alcohol(I think!!) But airlock isn't really moving its been 2 days, and I didn't know you weren't supposed to take off the lid!!! Ive opened and stirred it 2-3 times now. Any thoughts???

  • Not only are you not supposed to remove the lid, you should NEVER stir it it you do take the lid off. Why? Our friends, the yeasties, eat what they can, multiply and die off. When they die, they fall to the bottom. Let them. The only time Oxygen should be introduced to your beer is before you add yeast. FWIW, you are not smelling alcohol, you're likely smelling yeast. May 15, 2015 at 21:59

very simply - you have killed the yeast by adding it to the sugar solution while it is to hot, in my experience. dissolve in to the least amount hot water then add cold, if dissolving in a demi-john add an inch of cold first then half a kettle of hot water then sugar - then top up with hot till dissolved "DON`T COVER THE TOP" handle of a wooden spoon or swirl to mix sugar in to water. hope this helps

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