What does it mean when your S Shaped airlock has internal pressure

[BrewerB0B]

Hi I was looking at my wine's progress today and I noticed that in one of my carboys the pressure in the S Shaped airlock seems to be pulling the water to the right side instead of to the left side like it does when it pushes CO2 out. I've read that people prefer to use the S Shaped airlocks because they can see the pressure but I'd like to know what the different pressures mean. I assumed that when fermentation stops the pressure would just hang where ever it left off or maybe return to having an equal amount of water on both sides. Can someone clear this up for me? Thank you in advance, I have uploaded a picture to show you what it looks like.

 

[GilaMinumBeer]

Suckback.

 

[finsfan]

Possible change in temperature could do that. IF the wine is getting colder it would suck air in. I dont brew wine, but that is the best answer I have for you. Also, I would recommend filling your airlocks with cheap vodka. Water isnt sanitary and its not worth the risk of ruining anything if it all sucked back into the wine.

 

[BrewerB0B]

Thanks for the reply although there hasn't been a dramatic temperature change. I have a mead going that is still pretty active and another project, a 6.5 gallon bucket with cheap concentrated strawberry juice. I started the strawberry project after the mead but the bubbling in the airlock went from intense to nothing at all. I'm trying to understand why but I have read the air bubbling doesn't mean anything when it comes to brewing.

 

[dyqik]

It can also be atmospheric air pressure changes - 3 mBar difference (a bit less than 0.1" mercury) can push water up 1.2". Looking at the last week's data here on the edge of Boston, we've had a swing of >0.70" Hg, or nearly 10" of water.

Put an airlock on an empty carboy, and you've built a barometer

 

[finsfan]

I'm trying to understand why but I have read the air bubbling doesn't mean anything when it comes to brewing.

People new to brewing typically associate no airlock activity to their beer/wine before done fermenting. So when you see other members say not to watch it, that is why. It certainly indicates something (either fermentation or change in temperature) but shouldnt be the sole factor when deciding when to bottle something.

 

[Qhrumphf]

It also doesn't need to be a dramatic temperature change. The room or fermentation chamber changing a few degrees could do it, or if you're not adequately controlling fermentation temps (even in a fermentation chamber if you're only controlling the air temperature), as fermentation dies down the beer inside will drop in temperature (from above ambient due to the heat of fermentation and back down to ambient). That 5-10 degree change in temperature is more than enough.

If it were a dramatic change (say, ramping down to cold crash or to lager), it would likely be sucking some of that airlock liquid all the way up and over into the beer (hence the recommendation to use vodka)