Suck Back and Airlocks

[Zak2428]

I recently purchased a 7 cu ft chest freezer and an inkbird temp regulator which has been working great, but now that my fermenters are in a sealed location, I'm noticing that the airlocks are sucking back in alot of the liquid. It seems when I add more liquid to them, it drops again within 24 hours. I use 3-piece airlocks. I know the issue has to do with atmospheric pressures in there, but what are some ways to combat this issue? Is it even an issue?

I use sanitized water in my airlocks, sometimes vodka, so I know contamination is very unlikely. And, the water drops about half of what the airlock "requires" (photo attached). This is oddly the only fermenter that still showed bubbling with this suck back problem - not sure if it had to do with the StarSan solution I squirted in or what, but my other fermenters did not bubble after the liquid dropped. Is this something I need to find a solution to or does the amount of liquid leftover still keep my beer safe from Oxygen, CO2 release, etc.

 

[Ward Chillington]

OK, so you are fermenting in the freezer or cold crashing?

Suck back is typically a cold crashing issue, molecules are contracting and getting smaller as the beer cools down creating a vaccum effect but you are using a 3 piece fermenter ? Hmmmmm.....is the freezer "frost free" and you have some evaporative action going on that is removing the fluid in the airlock?

The liquid in the airlock is your barrier of air getting into the wort and beer.....think of it as a sort of a one way valve while you are fermenting pushing the lighter air out of the carboy. That coupled with the carbon dioxide that the yeast are creating while making your wort into beer for you is your second barrier to any airborne contaminates getting into the beer.

Are you using different yeasts in the batches you have in the freezer where your Lager yeast is going to like the cold versus an Ale yeast which likes it a little warmer?

 

[Zak2428]

OK, so you are fermenting in the freezer or cold crashing?

Suck back is typically a cold crashing issue, molecules are contracting and getting smaller as the beer cools down creating a vaccum effect but you are using a 3 piece fermenter ? Hmmmmm.....is the freezer "frost free" and you have some evaporative action going on that is removing the fluid in the airlock?

The liquid in the airlock is your barrier of air getting into the wort and beer.....think of it as a sort of a one way valve while you are fermenting pushing the lighter air out of the carboy. That coupled with the carbon dioxide that the yeast are creating while making your wort into beer for you is your second barrier to any airborne contaminates getting into the beer.

Are you using different yeasts in the batches you have in the freezer where your Lager yeast is going to like the cold versus an Ale yeast which likes it a little warmer?

Good questions - I have the temp sitting at 65 in the chest freezer. So there's no cold crashing. I used to be able to let the fermenters sit at room temp and it'd maintain around 68-70, but I recently moved and that's not an option anymore so that's why I moved to a chest freezer, with the inkbird and a small space heater, and with this new setup it's the only time i've experienced it.

At this temp, there's no frost and for the yeast, one fermenter is using a new yeast (Juice) and the other is SafAle US-05 (which I'm most familiar with) - both are in the desired temp range - both sucked in the liquid.

The wort, when I cool it and add the yeast is normally around 65-70 degree's also, so as far as I know, I'm not adding a hot fermenter to a 65 degree-ready chest freezer, so there shouldn't be a high temp fluctuation there either that would cause this.

 

[HighVoltageMan!]

This is a common problem when cooling beer in a carboy. The one piece will work better then the 3 piece in preventing any liquid from being sucked back into the carboy, but with both ways air will enter the fermenter. I know of only 2 ways to prevent this. First is the balloon method shown here:

https://brulosophy.com/2018/05/10/7-methods-for-reducing-cold-side-oxidation-when-brewing-beer/

Once it's cool it can be replaced with a standard airlock if you want. I did this for a while, but it was a huge PITA.

The second is to pressurize the vessel with cO2 prior to crashing. This is not only hard to do with glass or plastic, but it can be down right dangerous with glass since it's not intended to take any pressure. Kegs and some stainless steel vessels can be pressurized prior to crashing to keep a positive pressure in the fermenter.

The liquid getting back into the fermenter is not a big issue, but the oxygen ingress does harm beer. Most homebrewers just live with it or wait until it's keg to crash cool.

 

[Ward Chillington]

So you are fermenting and getting suck back?

 

[Donoroto]

I don't think the OP's issue is related to temperature: He puts the fermenter into a 65F environment, and even though it is still bubbling some of the air lock liquid is going missing.

In the photo I do not see that the liquid is being sucked back, the level in the 'inner' chamber is low and in the outer chamber it is high. Have you seen the liquid in the inner part rise to the level of the center tube?

 

[Mark Farrall]

Given enough activity the sanitiser will basically disappear. All the various materials added to allow it to coat surfaces make it more likely to climb out of the airlock and either drip or evaporate away. With a really active fermentation I find an airlock with sanitiser will disappear in a few hours. If I've got a beer that active I'll use a blow off until it settles down even though there's plenty of headspace in the fermenter and no chance of a blow off. Then change to an airlock later.

 

[Zak2428]

So you are fermenting and getting suck back?

Correct, it's just fermenting and the liquid is disappearing.

@Donoroto I have not seen the liquid rise above the center tube, I've only seen it at the level it started as and then the lowered amount shown in the photo 12-24 hours later. I've even added more liquid 3 & 4 weeks into fermenting (during secondary) and the liquid still lowers to this level...

I'll try keeping a closer eye on it the next batch rather than wait 12-24 hours. Was just hoping this was a common issue with a simple solution.. Fingers crossed it's just evaporating and my beer will not be affected.

 

[Craigerrr]

I have only ever had suck back when cold crashing with the one piece S type airlock, and one time when I had a blow off set up. Never had suck back with a 3 piece airlock.

 

[Head First]

Correct, it's just fermenting and the liquid is disappearing.

@Donoroto I have not seen the liquid rise above the center tube, I've only seen it at the level it started as and then the lowered amount shown in the photo 12-24 hours later. I've even added more liquid 3 & 4 weeks into fermenting (during secondary) and the liquid still lowers to this level...

I'll try keeping a closer eye on it the next batch rather than wait 12-24 hours. Was just hoping this was a common issue with a simple solution.. Fingers crossed it's just evaporating and my beer will not be affected.

It is common. It's evaporation as described by Mark. No worries. Just top it off once in a while. Before cold crash let it get low on sanitizer or use an s type bubbler.

 

[AHarper]

I'm not sure I fully understand this but... Has the freezer got such a good seal that any CO2 vented off the fermenter into the cavity surrounding the fermenter and not escaping out of the freezer then expanding to such a degree when the heater turns on to warm the interior causing the CO2 pressure to be greater than that inside the fermenter so it goes back into the fermenter i.e. blowback?
Is that what is happening? Would an additional hole in the Freezer with an external airlock fix the problem thus letting excess internal CO2 escape?
Am I totally misunderstanding the whole problem? I use a fermentation fridge with Inkbird and heater but have never experienced any blowback into the fermenter.

 

[Donoroto]

I have not seen the liquid rise above the center tube

Then it surely is rvaporation.

I have never used an airlock, I don't even own one. A blowoff tube is all I've ever used. I keep the end only about a quarter of an inch into the jar of liquid so when suckback does occur it isn't enough to fill the blow off tube and enter the fermenter

@AHarper No, Suck back occurs when the pressure in the fermenter is reduced compared to atmospheric pressure, such as when you cool the fermenter. The CO2 that's in the freezer will certainly leak out the seals which are not airtight

 

[Ward Chillington]

evaporation.....gotta be