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Implications of leaving air lock off fermenter during active

I am sure it’s been covered in these forums ad nauseam, but I have a quick question on fermentation and the lack of an air tight system.

The lid to my fermenter about a 6" in diameter opening blew off during it’s active phase and was left off and undisturbed for about six hours until I could get to Home Depot to get an appropriate sized blow off tube.

With that said there was tons of krausen (evidence on my floor) and the fermentation was still quite active when I woke up this morning (+10 hrs after blow tube was installed).

Is there any reason for concern at this point?

Not at all, the krausen will protect the wort from any bugs

Thanks Billy. I feel better now. I always get nervous when these things happen to my brews.


The krausen will also attract bug, like nats. So it is possible that the beer “could” become infected.

A good practice is to leave the bung and air lock in the drawer and start/finish with a blow off tube.

Thanks Nighthawk for the illustration regarding the blow off tube. I did have a blowoff tube for my carboy which worked well, but I switched to a Minibrew Affordable Conical Fermenter and my 1.25" nylon tube was too big to fit in the space provided. And unfortunately I was a pinch and I had to improvise.

In any case I am going to take the instructions shown in the link that you provided and make a b/o tube before my next batch. I guess I my have to bore the hole a little bigger to fit the 1" ID tubing.

Thankfully I did not see nats. We’re getting a little cold in SE Pennsylvania for them. I did see them once when I made a saison last summer though.

Question, do the sell anywhere a standard 1" bung with a 3/4" opening? I cannot seem to locate one anywhere.


i wouldnt worry about it… just wait it out… that happened to me and my lid blew off for… i dont know if it was 1 or 2 days… i just happened to walk by one day and notice the krausen everywere… i took a sanitized rag and cleaned up the bucket and air lock and pushed the lid back shut… the stout came out fine… now me on the other hand was not to fine when the significant other walked in while i was cleaning and saw how big of a mess was everywhere :slight_smile: cheers dont worry about it…

@ Garagelite wow two days!!! Ok, I feel much, much, much better now. I am going to take the previous posters suggestion and construct a nice blow off tube before my next batch to avoid this all together.


Yeah i dont know how long it was off but it only blew half way off. so cleaned it up and popped the lid back down, and cleaned the airlock. it was fine. im pretty sure it was atleast a day becuase i thought it messed up becuase there was not any airlock activity… after another day of thinking i actually checked the seal… it wasnt sealed… lol

If it was such a big problem, all of the open fermenters across the country, and Europe wouldn’t be making such good beers. It should be fine, as has been said, keeping the bugs out of it is the main issue once it comes off. I’ve had mine blow off a time or two myself without problems. Prost!

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