Air Lock

[Disco_tezz]

While Brewing my last batch of beer, which i bottled a week ago, I had the Airlock Start to suck air in. Instead of blowing the air out.

Just wondering if anyone knows why this would happen? and what problems this could cause to my brew?

is it still fermenting when this happens,

Cheers

Terence

 

[brettprevans]

While Brewing my last batch of beer, which i bottled a week ago, I had the Airlock Start to suck air in. Instead of blowing the air out.

Just wondering if anyone knows why this would happen? and what problems this could cause to my brew?

Cheers

Terence

I cant answer exactly the reason of why it was 'sucking air in', but it is caused by pressure variation ie the pressure outside the fermentor is greater than the pressure within the fermentor (physics). Airlocks bubble becuase CO2 gas is produced and need to escape. Gas is lazy and will find the easiest way out. if you are all tightly sealed then it will be through the sirlock hence the bubble. If you dont have tight seals, then the gas will most likely escape through there rather than your airlock and then there's less or no bubbling.

Back to your particluar issue. As fermentatio stops, the pressure inside and outside fermentor should return to an equilibrium (ie equal) or maybe even a little more outside pressure. thats fine. But the only time I have air 'sucked in' is when I lift my fermentor up after fermentation has completely finished. buts that a simple pressure variation.

As to why yours was sucking in air while fermenting i have no idea. unless the temperature iside the femrentor was a heap less than the temp outside. hot air expands nd cold air contracts, hence the pressure outside if hot would be far more than inside if cold. I suppose that could cause it, but without more info im not I can help.

 

[floppinab]

Hey Disco,

It's not all that uncommon at the end of a ferment if it coincidental with a reasonable temp drop inside your fermenter.

So firstly no it is most likely not fermenting anymore, assuming you have taking a gravity reading you can check and confirm that your wort has fermented out, all should be well. If you have a high ravity you may have a stuck ferment, that would be a problem.

Assuming your ferment has completed it has stopped producing CO2 and it cools down a bit, pressure reduces in your fermenters headspace (the area between your beer and the fermenter lid) and a slight vacuum is created and sucks in a bit of air.

As long as you are bottling/racking within a few days of this happening and your fermenter is not in a very nasty spot (i.e. next to an uncovered overflowing bin thereby potentially exposing your beer to a lot of potential infection nasties!!!) you should be fine.

One other tip, depending on what type of sterilizer solution you use (Iodophor or the silver solutions probably OK, bleach probably not) is to use a bit of that liquid in your airlock instead of water. It won't completely sterilize the air going into your fermenter but it probably helps a bit.

 

[Pandreas]

Disco.... No idea why this is happenning.

I would be just a little concerned about infection risk, however, if the water from your airlock is splashing into your fermenter.

I once had a fruit fly die in my airlock. I left it there for days and then decided to take a sample to test the SG. I opened the tap to draw out some of the wort and didn't remove the airlock first.

This got the airlock working in the opposite way as air was sucked into the fermenter from outside. Lots of airlock water got in my fermenter. I didn't end up with ACETO infection, but this was probably just luck.

 

[Disco_tezz]

One other tip, depending on what type of sterilizer solution you use (Iodophor or the silver solutions probably OK, bleach probably not) is to use a bit of that liquid in your airlock instead of water. It won't completely sterilize the air going into your fermenter but it probably helps a bit.

Thanks for the responses, I figured it was something as simple as a change in air pressure or something like that, but just wanted to make sure,

As for the liquid in the airlock, i do use the sterlizing solution in it, as it makes sence to use that.

cheers everyone

 

[brettprevans]

AS the other have said, its probably just a normal reaction to the fermentation being finished. Use your hydrometer to check.

As to the water in your airlock, that's why its there, to help minimise the risk of infection while letting out CO2 gas. Cooled boiled water is the best thing to use in the airlock (maybe with some sanitiser if its one thats doesnt need to be rinsed off as it wont affect the beer). I make sure theres plenty of water in my airlocks so that the air will never getinto my fermentors.

Your brew should be fine

 

[chris.taylor.98]

I have had this happen to me at the start of fermentation.

If your yeast does not have enough oxygen to propagate properly, it can cause a back pressure build up inside the fermenter, causing it to try and suck more air in.

This could be a sign that you are putting the yeast under stress and it might lead to some off flavors being produced as well as incomplete fermentation.

I have found this to be the case mainly with higher gravity beers ( > 1.060 ) where you really do need to consider aeration ( and yeast health generally ) more carefully.

Since I have started to aerate the wort with a diffusion stone, I have not been having this problem.

 

[brettprevans]

If your yeast does not have enough oxygen to propagate properly, it can cause a back pressure build up inside the fermenter, causing it to try and suck more air in.

I have found this to be the case mainly with higher gravity beers ( > 1.060 ) where you really do need to consider aeration ( and yeast health generally ) more carefully.

Since I have started to aerate the wort with a diffusion stone, I have not been having this problem.

Aeration is a very important part of making beer. We should point out that while it is important to aerate your beer BEFORE you pitch the yeast. once pitched you dont want to aerate the beer at all unless you want to risk infection and other nasty things.

I just stir the crap out of my beer and get a whirlpool going for a few mintes. really mix everything and aerate. if I have a spare fermentor and im doing a small specialty batch (say 15L) I will pour the brew between the 2 fermentors to really aerate the buggar.

Good point Chris about the need to aerate high OG beers otherwise it can lead to unfinshed fermentation.

 

[wildschwein]

I find that suck back is a sign that fermentation has finished. Not always but usually. I never use a hydrometer (broke it years ago). Once the bubbling in the airlock has finished (about 10-14 days in winter) I find that suck back occurs and the contents of the 1st chamber eventually gets sucked back into the 2nd. When it stays like that for a day or 2 I bottle. Haven't had an explosion or gusher yet. On a couple of occasions, and this is rare, I have seen early suck back. It was usually too early for feremtation to have been finished so I just left it and the bubbling started again. I'd always assumed that when the yeast is finished its job it would be trying to get some O2 for storage and thats why the airlock sucks back. I'm not really sure about this theory though, but suck back does tend to correspond with the end of fermentation in my experience.

I use some of my sanatising solution (bleach solution) in my airlock and find there is an equilibrium amount that the airlock likes. If I overfill it, it just spits out the excess and achieves the correct amount by itself.

 

[pint of lager]

To avoid sucking airlock fluid into the fermenter, just use a small amount of fluid in the airlock, rather than filling it to that little line. If leaving stuff in the fermenter for weeks, watch out for it drying out.

Or use a two part airlock.

 

[chris.taylor.98]

Good point pint of lager.

I only put the bare minimum of fluid in the air lock, as there is also evidence that the yeast ferments better in lower pressure environments.

I actually going to try an open fermentation on my last batch, but had yeast issues (long lag time) so chickened out.

I heard a podcast recently where they doing side by sides on different fermentation vessels (conical, plastic fermenter, glass carboy and open glass carboy). The open glass carboy scored consistently higher than the other fermentation vessels even thought they where all brewed with the same wort and yeast.

In regards to sanitation of the airlock liquid, I usually just go with boiled water.

I probably would not use bleach water, as the bleach will causes issues for the yeast, and can contribute to off flavours, although the amount that would get in there is small enough not to worry about it too much.

You could use something high in alcohol (vodka?) if you are really worried about it.

 

[wildschwein]

Yeah it's only an issue if the water from the airlock gets pulled back into the beer but on my lock it's pretty hard to make that happen. The suck back only reaches the 2nd chamber and doesn't pass back into the beer. Point taken though, you don't want bleach in your beer.

 

[petesbrew]

Took a sample last night, and the airlock water bubbled back into the fermenter. As I heard the not so good action I thought of this thread.
oh well, shit happens, I'll try to remember next time.