Author Topic: Over foamy but under carbonated???  (Read 15488 times)

Offline mworlund

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Over foamy but under carbonated???
« on: October 29, 2014, 05:34:05 PM »
Not sure how to deal with this. I have a new kegging system. Pretty basic, regulator, 5G CO2, 5G corney keg. Trying to get to 2.3 carb (as per BeerSmith). Started 10 days ago and have all foam when I pour. Once it settles out it is pretty flat. Turned the pressure completely off the keg 24 hours ago to see if that would help. Still heavy pressure and all foam. Read one forum that said DO NOT relieve the pressure in the keg as it will cause off flavors so, I haven't done that. Too much conflicting advice out there so I really don't know what to try next.

Anyone that has had this experience, I would love to hear from you.


Offline TAHammerton

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Re: Over foamy but under carbonated???
« Reply #1 on: October 29, 2014, 08:17:56 PM »
What temp is  the keg at? Sounds like it is not cold enough.

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Offline JohnnyMac

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Re: Over foamy but under carbonated???
« Reply #2 on: October 29, 2014, 09:33:56 PM »
Did you overfill your keg and not allow sufficient head space to get enough CO2 to carbonate ?


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Re: Over foamy but under carbonated???
« Reply #3 on: October 30, 2014, 03:22:58 PM »
Sounds like you are overcarbonated.  How long has it been under CO2 and at what pressure and temperature?

Offline Maine Homebrewer

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Re: Over foamy but under carbonated???
« Reply #4 on: October 30, 2014, 03:42:51 PM »
Try bleeding off some of the pressure before you pour, enough so that it barely pours out, then bump it back up when you're done.
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Offline brewfun

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Re: Over foamy but under carbonated???
« Reply #5 on: October 30, 2014, 07:29:17 PM »
Foaming is the number one complaint with home draft systems. There are a lot of reasons why draft systems foam. The main ones are temperature, line size and pressure. The symptom you're describing sounds like it's not "laminating." This is the term for CO2 being in the beer and released slowly over time.

The carbonation temperature helps determine how much gas is absorbed by the beer. There are lots of tables around to help you determine this for the right level. The colder a beer is, the more CO2 is wants to absorb. If you carbonate at a higher temperature, as the beer cools, it'll absorb more.

If there is a big swing in temperature within the line or into the glass, the beer will foam. Make sure your draft tower has cold air going into it. The shanks should be long enough that they conduct cold from the keg chamber.

The first part of pressure is that pure CO2 dispense pressure needs to be the same as the carbonation temperature. This maintains equilibrium with the beer. Again, refer to the CO2 charts and make sure the beer is at the proper temperature for the pressure.

Constant release and repressurization of the beer causes loss of head retention and can promote oxidation staling. The proteins used in head retention only work once and even though there are lots of them, it takes its toll. Often, you'll see tiny white floaties in filtered beer, which form because of too much foaming. They also form in stale beer.

Line Length
This is where the first two items need to come together in creating the system. The dispense pressure needs to equal the resistance of the line plus height of the tap, minus one pound. So, to put it another way, the line length needs to be matched to the dispense pressure.

What's the resistance factor?
Resistance values will change based on what the line is made of. This is for the inside diameter of vinyl, the most common used in brewing:

3/16" (4.75mm): 3.0 PSI/ft. (67.9 kPa/m)
1/4" (6.35mm): 0.8 PSI/ft. (18.1 kPa/m)
5/16" (7.94mm): 0.4 PSI/ft. (9.0 kPa/m)
3/8" (9.53mm): 0.2 PSI/ft. (4.5 kPa/m)

The simple rule is the bigger the diameter, the less resistance. Simple, right?

Putting it Together
From a carbonation chart, we see that a beer kept at 40F (4C) will need just 12 PSI to maintain 2.5 volumes.
From the list above, we can see that 1/4" tubing has a resistance of 0.8 PSI

To get the right length of 1/4" ID tubing, we want to divide the dispense pressure, minus one pound, by the line length.

12 - 1 / 0.8 = 13.75 feet. That's a lot of tubing!

Looking at 3/16" ID tubing, we get:

12 - 1 / 3 = 3.6 feet. Much more reasonable length!

I've simplified this formula a little because I haven't included rise pressure or other hardware. The differences are small, so a rule of thumb is that about four feet of dispense hose and ~14 PSI is perfect for most applications.
Beer Appreciation is the space between pints.

Offline twhitaker

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Re: Over foamy but under carbonated???
« Reply #6 on: November 03, 2014, 07:24:41 PM »
I often found that my kegs over carbonated after a few weeks. I turned the pressure right down, pull the relief, and add just a bit of pressure until the beer just flows out. After a few glasses things were ok.
Since then, Once the beer is carbonated, it only needs a bit of pressure to make it flow out. I turn off the gas and bump it as needed when the flow slows down, keeping pressure set at 8 psi.. temp always at about 34 F- cold!
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