Blowoff Tubes and PET Carboys

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Feb 1, 2017
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I have a couple 5 gallon PET carboy's that I need to use for primary fermentation. The opening fits a #10 stopper, so the normal 1" diameter tubing I have is out of the question.

I've seen some people using some smaller tubing right in in the stopper opening - is that really the best/only blow-off tube solution when the carboy opening is that large?

Just get the other style of airlock that is not the “S” style a lot of people use. The 2 piece airlock is much better imo and you can hook up a hose straight to it - that’s what I do.
This works on both the pet stoppers and the universal one. the raised part that the air lok fits into has an outside diameter that a 1/2" silicone hose will fit over if you heat the end up in boiling water and press and twist. This way you get a larger hole,and it's brewery tubing. The plus is the hose fits my faucet adapter for quick disconnect and can be flushed with hot water.
What I do is...I cut a few short sections (2 inch) off an old plastic racking cane. I stick one of those into the stopper then attach some 3/8" ID tubing to that (pic below). That worked for me the last time I had a blowoff. Looking at the pic makes me wonder if some 1/2" ID tubing would fit over that small nub on that style stopper. You could also drill a larger hole into a solid #10 stopper and use something like a 1/2" ID tubing.


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