Small suck back in blowoff tube no cold crash

[DangersBrew]

Fermenting a Belgian and been fermenting it at 68 for two weeks. Noticing a small amount of suck back in the blowoff tube and havent cold crashed. Wondering what can cause the star San solution in the blow off jar to be creeping up the blow off tube without any significant temperature change.

 

[davidabcd]

I don't know what else would cause the liquid to reverse course besides temperature, height or pressure on the vessel. Maybe a photo of the setup would prove useful to others attempting to diagnose.

 

[DangersBrew]

It’s a spike flex plus and I have my glycol chiller above it. It was weird too before I pitched my yeast I brought my temp down to pitching temps 68 then connected my blow off tubing and before fermentation began there was small suckback halfway up the tube when I checked the next morning. I ended up disconnecting it and got the suck back in the fermenter before the fermentation began to equalize the pressure. Just weird. I just raised the temp to 70 and seems like it equalized. But Here’s my Setup for reference.

 

[davidabcd]

Setup

Very nice setup. I am stumped on the problem though; hopefully, someone can point out why it occurred. One good thing is that a little Star San in the batch isn't a big deal.

 

[DangersBrew]

Thank you it’s been a long time in the making. I appreciate the response.

 

[Brew_Dude41]

I am just guessing here, but could it barometric changes or even temp changes the environment that the are causing it? Where is your set up located?
If you are in a garage that is subject to drastic swings in temp, that blow off hose (and the air in it) might be heating and cooling enough to cause that minor amount of suck back.
Not sure if that would be enough draw up the starsan, but that is my guess.

 

[DangersBrew]

Thanks Brew, Yea my setup is in a garage. It hasn't done this with previous batches. I agree maybe since it’s getting warmer during the day and cool at night that could cause it.

 

[segallis]

Besides temperature variation, ambient barometric pressure can vary by anywhere from 0.3% to as much as 3% if a front is approaching. Our local pressure on a typical Florida day today changed by 1.3%, so that would cause a 1.3% difference in volume inside the fermenter (which is about the same volume variation a 5 degree F delta temp would cause). Plus any actual temperature variation would add to that.

 

[Plop]

Could it be because of yeast activity?
The fermentation starts, the temperature rises because of the activity.
The activity then stops when the fermentation is over causing the temperature to drop.

I had a quad fermenting as high as 26 degrees C (79f) while the room temp was only 18c (64.5f).

 

[Elric]

I’ve had suck back before with just ambient temp changes/temp change as fermentation slows. Oddly have only ever seen it with metal fermenters…