Cold crash suckage?

So I just cold crashed for the first time. 3 days at 36 degrees. When I went to keg it (an all columbus IPA) this evening I noticed that my blow off jar was running low. Now I can't say I remember how much was in it when I cranked down the temps - it's been in there a total of 25 days so some evaporation is normal.

Then I remembered these threads about the sanitizer in air locks being sucked in when you cold crash. Did the same happen to me here?

Here's how my setup looks. You can see the blow off jar is on the shelf behind the carboy:

I should also mention that the top 1.5" or so of the beer looked much clearer than the beer below it. I tried as hard as I could to not siphon that into the keg. All in all I estimate I pulled just over 4 gals out. I lose about a half to trub and the level was just above the 5gal mark but I didn't think to check it against this picture so I don't know if it was in fact higher or not.

Yup, sounds like a case of suck back.

igotsand said:

Yup, sounds like a case of suck back.

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Crud!

Any chance I can still drink what I siphoned out as I stayed below the clearer level?

Also, how do I prevent this? I thought using an airlock would always have suck back...I didn't think it would happen with a blow off but admittedly I didn't think about it much. Until now.

Carlscan26 said:

Crud!

Any chance I can still drink what I siphoned out as I stayed below the clearer level?

Also, how do I prevent this? I thought using an airlock would always have suck back...I didn't think it would happen with a blow off but admittedly I didn't think about it much. Until now.

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You can prevent it by using a bung cap(?), or whatever its called...
It's happened to me before and I still drank the beer(the suck back was starsan)..you won't die from it, it will make your beer watery tho...
What was in your blowoff bucket?

igotsand said:

You can prevent it by using a bung cap(?), or whatever its called...
It's happened to me before and I still drank the beer(the suck back was starsan)..you won't die from it, it will make your beer watery tho...
What was in your blowoff bucket?

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Thanks! It was Starsan. I just drank my measurement sample and compared to a sample off the bottom of the carboy after kegging. The dregs are watered down at best. The sample I pulled seemed decent.

I'll look into getting a bung cap thing then before I try this again.

Yeah, the lessons we learn..betcha you won't do that again!

igotsand said:

Yeah, the lessons we learn..betcha you won't do that again!

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Not this mistake anyway.

I like to use my better bottles when I cold crash because I have the "dry taps". They are a positive pressure only, waterless air lock. No suck back ever. They cost an arm and a leg but they are worth it.

+1 for the thread title.

FermentNEthinG said:

I like to use my better bottles when I cold crash because I have the "dry taps". They are a positive pressure only, waterless air lock. No suck back ever. They cost an arm and a leg but they are worth it.

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Now see - this may be the final straw for why I'll *have* to get some new carboys with ports and all the fittings lol

Why not just use a 1-way liquid/gas check valve in line with the blow off tube? You can get some on US Plastic for just a few bucks. I suppose they could possibly get clogged up if a bunch of particle matter gets shoved up through there. But at worst it's something cheap to hook up to your 3 piece air lock or tube after fermentation is done and you want to cold crash.

I use an S type airlock for cold crashes and don't get any sanitizer in the beer.

I may have to get a couple of those type of air locks. I have the three piece type. I just kegged a batch this morning that I cold crashed. I don't know if it sucked anything back or not. I had rum in mine, so either way it's a win.

Does the height of the blow off container make any difference? For instance if mine had been lower than where mine is at would this not have happened?

FYI - my beer tastes great, got a lot of compliments on it this weekend. So either I had less suckage than I thought and/or I was able to siphon cleanly enough.

Randy_Bugger said:

I use an S type airlock for cold crashes and don't get any sanitizer in the beer.

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This is what I do, but these can suck back too. When you use these, you don't need much more water than what it takes to cover the lower "u." The more you put in it, the more likely it is to suck back.

Randy_Bugger said:

I use an S type airlock for cold crashes and don't get any sanitizer in the beer.

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Correct me if I'm wrong, but an airlock is a two way street. Under even pressure levels oxygen couldn't push it's way through the airlock and into your beer, but if a vacuum is created within the carboy, as a result of a decrease in temperature, it would certainly suck oxygen into the carboy. Even if you still have sanitizer in your airlock after cold crashing oxygen could still have come through the solution and into your carboy.

DrunkenNightsPodcast said:

Correct me if I'm wrong, but an airlock is a two way street. Under even pressure levels oxygen couldn't push it's way through the airlock and into your beer, but if a vacuum is created within the carboy, as a result of a decrease in temperature, it would certainly suck oxygen into the carboy. Even if you still have sanitizer in your airlock after cold crashing oxygen could still have come through the solution and into your carboy.

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I would say yes, oxygen could get pulled into your fermenter. I would believe the blanket of co2 already in there would mitigate that risk though. Sanitizer getting in there is another story.

Carlscan26 said:

FYI - my beer tastes great, got a lot of compliments on it this weekend. So either I had less suckage than I thought and/or I was able to siphon cleanly enough.

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Or...... perhaps Starsan should be part of the ingredients for this recipe!!!???

An S-Airlock wit vodka is great for cold crashing.

I've had a similar issue with cooling wort in a fermenation chamber before pitching yeast using a 1" blowoff tube. To solve this I've marked a canning jar the the height to fill it with starsan that doesn't fill the 1" tube more than about 18" tall. If the starsan gets pulled up by vacuum, the vacuum will break before starsan gets high in the tube. The downside to this is that you blowoff container is small and I put it inside a small bucket to contain a blowoff mess - pretty rare...