Homebrewing - Beer, Mead, Wine, Cider

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Absuing a keg as a bung valve (i.imgur.com)

submitted 3 months ago* (last edited 3 months ago) by [email protected] to c/[email protected]

5 comments fedilink hide all child comments

As my latest batch is already quite the experiment, I decided to even go a little further and not use a traditional bubbler to vent off CO2 from my bucket this time, but opt for a keg to do that.

The rubber seal in the hole of the bucket‘s lid takes a 9.5 mm hose snugly, which connects to the gas intake of a keg filled with a good 5 litres of disinfectant. The keg’s liquid out has a line attached to go into the depicted 5 litre can.
This way, at the end of fermentation, I’ll have a sanitised keg & can, and the keg is already full of CO2. Also, should I experience suckback from changing temperatures (mind you, my setup lives in my garage), there is a buffer of CO2 in the keg for that, and the line into the can is the one I use to package from the bucket, so it’s nice that it gets sanitised along the way too.

What do you think? So far, my only concern is how much pressure buildup is required to displace the disinfectant from the keg and if the bucket's lid with the attached hosing is tight enough for that.

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[–] [email protected] 4 points 3 months ago (1 children)

I just did the conversion, and 1 psi = 70 cm h20. That means you only need less than a psi to get the sanitizer moving. I think the bucket can likely hold that. You might want to add weight to the lid to make sure there's no leakage from the outside edge of the bucket.

[–] [email protected] 3 points 3 months ago (1 children)

Thanks for the calculation! It didn’t cross my mind to roll the numbers, that’s quite reassuring.

Thinking about everything now, I think I should elevate the can to the level of the liquid post of the keg, to avoid a siphoning effect where all the sanitiser goes through the line in one go once it gets into motion. 🤔

[–] [email protected] 3 points 3 months ago (1 children)

That probably shouldn't happen, cause it would pull a vacuum on your beer (wonder what effect that would have). It might be able to pull a siphon for a short time, and then cut off. You would then have like an oscillation of pressure on your beer which probably isn't ideal. Definitely a good move to put the can higher.

I wonder if there's a good way to prevent any siphoning from going the other way.

[–] [email protected] 2 points 3 months ago

Uh, I haven’t even thought about the possibility of reverse siphoning. Maybe better I’d better leave the can where it is? To my understanding, siphoning "uphill" is way harder (if even possible at all, given a specific liquid, height, tube diameter etc). The possible pressure oscillation sounds less "threatening" to me right now.

[–] [email protected] 1 points 3 months ago* (last edited 3 months ago)

Update: Yeah, dang, it doesn't work as I expected.

Observations: The lid bulges, but barely any movement of liquid happens. I had to press the lid really hard to get the slightest flow towards the can going at the beginning. It's barely even trickling now that the line is filled with liquid. As this is going to be a rather light beer, I don't expect much more CO2 buildup, so this really isn't ideal.

Theory: The buffer of air is too large. The CO2 from the fermentation increases the pressure in the system, but not beyond the compressibility of the gases involved. Applying pressure to the lid took a lot of force and felt like squeezing a large half inflated ball. Also, some of the CO2 may have dissolved in the StarSan solution.

Now I hope I have not spoiled my beer by at least theoretically exposing it to all the oxygen from the headspace in the keg. I'll probably get a bubbler ready tomorrow and just purge the keg with CO2 from a regular source.
Most of this setup sets me right on track though to do a oxygen free transfer though, so not all was in vain - in case that I haven't spoiled my brew. /o\

The only possible fix that I can think of might be using a fermenter that is actually rated for pressure and doesn't "inflate" like my plastic bucket, but I'm not sure how much that actually contributes. Brewing a bigger beer with more generated CO2 would probably also be advantageous.