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Kegged beer tastes slightly sweet on the second day (not the first)

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Hi everyone,
I've been homebrewing for about a year, and done about 20 5gal batches so far, and bottling.
Never had a bad batch bottling - beer was so good it made me want to start a brewery.
Then just a few months ago, I upgraded to a 4x Keg system which I installed taps into a fridge.
A single C02 cylinder, single regulator is stored outside the fridge, with a low pressure air line going into the side of the fridge into a 4x air block, from the air block to each of the kegs.

Here is where my problems began...

After getting the kegs, I followed the standard sanitation practices i did with bottling, using a PBW solution in the keg, pumped it through the lines, then sanitized with iodophor, and pumped it through the lines.

Setup information: Keg pressure is 10psi, Taps are at level with top of the Keg, Beer lines are approximately 4ft.

Keg 1: Kegged a cider, was great.

Keg 2: Kegged a pale: went all kinds of wrong.
History:  Tasting out of primary, tasted good, tasting out of secondary tasted fantastic. Kegged and naturally carbonated using 1/3 cup dextrose. Left 3 weeks, then refrigerated, and hooked up CO2 @ 10psi.
First Day: taste was flat (like it didn't carbonate), but it tasted fine (not sweet)
Second Day: tasted kind of sweet, excessively foamy (all foam, no beer)
As time progressed, it got sweeter and sweeter (I left the C02 hooked up, just in hopes it would get better)

Keg 3: Kegged a Ginger Ale, Force carbonated, tastes fine, no excessive foam (no excess sweetness is noticed, however it is HEAVILY ginger-fied, so this might be covering up any sweet taints)

Keg 4: IPA, naturally carbonated using 1/3cup dextrose, pressurized keg lightly to ensure there was a seal on the top this time (as opposed to Keg #2)
Let sit for 3 weeks. measured pressure in keg before refrigerating (pressure from C02 pressure + carbonating pressure)
After refrigerating, hooked up to CO2 line, tastes great, slight sweetness, but masked by intense hop aroma and flavor... this beer is good, but could be better (that hint of sweetness bugs me)

Keg 1 of cider, ran out.
Cleansed and Sanitized Keg 1 and lines and tap.
Kegged a light ale, this time force carbonated (as all of my natural carbonations have failed either terribly, or were so so).

I charged it with 10psi, then let it sit in the fridge overnight to get down to about 34 degrees. Then I used a second C02 bottle and pressurized the keg to 40psi, and shook the keg till no more C02 would come out of the cylinder (this was done audibly from the regulator).  I let it sit overnight, then did the same thing the following day, then I let the beer sit overnight again.

The 3rd day, I purged the air, and connected it to my 10PSI line, and pulled first draft.
It was overly carbonated (it hadnt been at 10PSI for long at all), so I figured it needed time to equalize. But it tasted great - crisp and dry (no sweetness)

I let the keg sit, then today is Day 2, I pulled a sample, and it still foamed up (all foam, no liquid) - obviously it was flat when it settled, however - it has started to develop "the sweetness"
Its driving me crazy.

So this brings me to my questions:

1) Could a "sweet" beer in another keg (I'm thinking Keg #2) taint a beer in another keg (thinking Keg #4 and the second use of Keg#1 above)

2) Has anyone ever experienced this before?  I have been searching and cannot find any hints so far

3) When kegging and trying to naturally carbonate, has anyone had a problem keeping a seal and the beer failing to carbonate? (referencing Keg #2 and Keg#4 above)

Thanks for all your help!


First off, welcome to the forum! I will admit that I did not read your entire post but let me try and help from what I have gatrhered.

First off, Co2 should make a beer taste drier, not sweeter. The more carbonation the drier the beer should be perceived. This would make sense, except you said the beer tasted flat first, then got "sweet" as it carbonated. Which is oddm because this is backwards. It could be that you are picking up some oxidation which is giving you this perceived off flavor. Or, perhaps this "sweetness" is more like butterscotch? That would be caused from diacetyl which can be brought on by a  number of things, usually fermentation issues. But if the beer tasted fine in primary and secondary the it could be caused from either oxidation or an infection.

But, since it is really hard to pin point exactly what is going on here let me give you a few pointers.

#1) You don't really need to secondary a beer that is going to go into a keg. The keg itself acts as one big seocndary, only better = because you can purge the o2 with co2. When you tap the beer you ca blow out the initial yeast and not worry about seocndary (or transfer into another keg off the yeast via a jumper). If you insist on using a secondary use a keg. 100xs better than a glass carboy.

#2) Co2 is Co2. It tastes the same whether it comes from force carbonation or natural. Try simply hooking your beer up to the co2 at ~12 psi and letting it sit at serving temps for 5 days. It will balance out and be pefectly carbonated. Using sugar is fine but you could run into inconsistencies. Hooking up to co2 and carbbing that way guarantees perfect carbonation every time.

#3) Look at the off flavor trouble shooting guide here: and see if you can more accurately identify this "sweetness". If "sweetness" it actually is it may be you priming sugar not fermenting all the way. Haard to say.

I will check up on the off-flavor guide. I have read a lot so far online but have not been able to identify the flavor yet.

Looking at your Point #1:

When you say use the Keg as a secondary, do you hook an airlock to the air side of the keg (and carbonate later)?
Or do you let the keg build pressure and carbonate during secondary?

Thanks for your help!

I read all of it. Never used dextrose before. My current practice is to add 3oz of cane-sugar to the keg. I think if you're getting a progressively sweeter beer from time to time then something could be covering up the sweetness. The "cloudier" initial pints give way to clear beer, sometimes distressingly near the end... :-[

I find the cloudier and more yeasty pints are more bitter than subsequent draws. Everything is dropping down in a keg. Could be you need to let the keg sit without shaking. Don't know if this even helps with your problem.

I rack around 10 or so days after a gravity check onto the sugar. The keg sits for a couple weeks or more. The resulting carbonation is perfect and the beer is almost clear by the second glass. It's a safe way to carbonate that doesn't require hooking anything up except for the initial blast to seat the cornie lid.

Paul you never mentioned how you brew. Is it grain or extract?

I typically do extract based beers, or a partial mash with extract.

Since I am currently using a secondary fermenter rather than using a keg as secondary, I often have very little yeast sediment in the keg.

So my biggest question (listed in the initial post):

On a multi-keg system, where the same CO2 line is connected to each keg at the same time. Can beer flavor from one keg travel through the lines to "taint" one of the other kegs?

My intuition says no because the aroma is not potent enough to permeate the liquid - but I've been plenty wrong before.  If I can concretely say this cannot happen, then I can at least narrow it to contamination or oxidation (odd that I've never had these problems before kegs, but these flavors certainly don't come from no where).


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