Kegs Holding CO2 but Leaking Liquid (?!)

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Iowa Brewer

Iowa Brewer

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Hey all,

Bought a pin-lock keg from a very reputable online store, purged CO2 it came with, & filled it with StarSan. After letting it sit for a few, I tipped it on its head to sanitize the top and, to my surprise, StarSan slowly leaked out of the mouth seal!

Wondering how a keg that held CO2 moments earlier was leaking liquid, I replaced the O-ring with a new, lubed one, but it kept leaking.

So I took another keg of mine, purged the CO2 I had in there for storage, lubed the O-ring, filled it with StarSan, and the same dang thing happened! Even after holding CO2, the mouth leaked liquid.

Any ideas on what could be going on? To quote Jacobim Mugatu (Will Ferrell's character in Zoolander), "I feel like I'm taking crazy pills!"

Thanks for any advice/insights you can give
 
I wouldn't bet that a new-to-anyone keg arrived pressurized with CO2 when air is cheaper.
I use my compressor to test kegs, not my CO2 supply.

Anyway...if a keg is prone to leaking liquid when inverted you better believe it was leaking CO2 when upright.
Gas molecules are what we call "very, very small", compared to liquid molecules ;)

And remember the primary usage model for these kegs was to hold soda syrup in post-mix applications or finished soda in pre-mix applications, sitting upright, under significant pressure that served to pin the lid tighter than the lid bail can manage in an aged keg...

Cheers!
 
[Additions]
Most corny kegs need some pressure (6-12 psi) to make the large rubber lid o-ring seal. IOW, the lid seal is prone to leaking under low or no pressure. You could also tighten the bail a bit, that may help. But you'll need a vice and a long wrench while applying some hulk strength in the right direction.

Or stick a dime or penny under the bail legs where they meet the bottom rim of the mouth.
 
day_trippr said:
I wouldn't bet that a new-to-anyone keg arrived pressurized with CO2 when air is cheaper.
I use my compressor to test kegs, not my CO2 supply.

Anyway...if a keg is prone to leaking liquid when inverted you better believe it was leaking CO2 when upright.
Gas molecules are what we call "very, very small", compared to liquid molecules ;)

And remember the primary usage model for these kegs was to hold soda syrup in post-mix applications or finished soda in pre-mix applications, sitting upright, under significant pressure that served to pin the lid tighter than the lid bail can manage in an aged keg...

Cheers!
Click to expand...

Great point about pressure being needed!
 
IslandLizard said:
Most corny kegs need some pressure (6-12 psi) to make the large rubber lid o-ring seal. IOW, the lid seal is prone to leaking under low or no pressure. You could also tighten the bail a bit, that may help. But you'll need a vice and a long wrench while applying some hulk strength in the right direction.

Or stick a dime or penny under the bail legs where they meet the bottom rim of the mouth.
Click to expand...

cheers! What are bail legs?
 
day_trippr said:
No.
Click to expand...


so when i'm doing my 'hobby' chemistry projects, weighing things out....i've been doing it wrong this whole time? i mean acetic acid has around a 60 gram a mol weight, citric acid like 200 grams a mol, so if i was going to make a neutral solution of baking soda with a mol weight of 84g's a mol? you need to know how many molecules are in a given weight of the stuff....

but back to the leaky lid...

https://www.amazon.com/Cornelius-Re...ocphy=9030249&hvtargid=pla-633828019340&psc=1
i've had plastic feet get worn out before....
 
day_trippr said:
You are comparing a gas phase substance against a liquid and apparently claiming the gas is denser? 🤔
Click to expand...


no...i'm just trying to sound smart! but i was thinking about it along those lines..... we've got a keg that apparently holds co2, but upside down leaks liquid,,,,


so upright the gas would be sealing the lid, but upside down, the gas would be pushing the liquid onto the lid?

edit: and my response as far as i know was accurate? there are less molecules in a gram of co2 then water?
 
"apparently holds CO2" is the error in that thought.
Seriously, a keg that leaks liquid inverted was leaking gas while upright.
Prove me wrong...

Cheers!
 
day_trippr said:
Prove me wrong...
Click to expand...


i can't honestly...but this is a thread saying that's what's going on...

edit: trying to get some star trek techno bable to go along with it..... :mug:

edit 2: just to get the creative juices flowing...this is a pin lock keg? what kind of prv does the lid have?
 
Last edited:
sibelman said:
If the full, inverted keg was sitting on its own lid, even partially... This might defeat the seal and allow leakage of fluid molecules, irrespective of molecular weight or gas vs liquid phase.
Click to expand...

Good point sibelman!
However, it did this as I held it up to ensure the leak was coming from the mouth and not one of the posts.

I’m guessing it’s the lack of pressure, which I’m going to test
 
bracconiere said:
how many molecules of a substance are at a given weight...
Click to expand...

I think you kind of mis-phrased this. The molecular weight of a molecule is how much, in grams, 1 mole of the substance weighs. 1 mole = 6.02x10^23 molecules.

bracconiere said:
lol, i'm just saying water has a way smaller molecule!
Click to expand...

Water molecules are smaller than CO2 (lower molecular weight), but I don't think the lid is sieving out the CO2, allowing only the water to pass. That kind of a filter would have to be far more complicated than an O ring with some keg lube.

:bigmug:
 
marc1 said:
I think you kind of mis-phrased this. The molecular weight of a molecule is how much, in grams, 1 mole of the substance weighs. 1 mole = 6.02x10^23 molecules.



Water molecules are smaller than CO2 (lower molecular weight), but I don't think the lid is sieving out the CO2, allowing only the water to pass. That kind of a filter would have to be far more complicated than an O ring with some keg lube.

:bigmug:
Click to expand...


molecular sieves can do it? lol, does the lid get warm?
 
Was the keg pressurized when you inverted it or just filled with StarSan? Most of my kegs leak StarSan from the lid when inverted and unpressurized. However, they do not leak when pressurized (gas or liquid). At the same time, I have never inverted a pressurized keg.
 
pvpeacock said:
Was the keg pressurized when you inverted it or just filled with StarSan? Most of my kegs leak StarSan from the lid when inverted and unpressurized. However, they do not leak when pressurized (gas or liquid). At the same time, I have never inverted a pressurized keg.
Click to expand...

That's exactly what happened, pvpeacock!
 
Dang! Thank you all for the feedback, and some of the best/funniest back-and-forth banter I've seen in a long time 🤣

So, here it is. It was the lack of gas pressure to create the seal. Never ran into this before, but there it is. Thanks again, all!

I'm going to keep that pennies under the bail feet trick in my back pocket, though.
 

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