Expert: Spencer W Thomas - 4/4/2011

Question
So I just tapped a keg, and when trying to extract the beer all I am getting is foam for a long time now, the beer is cold, I have released a lot of the pressure from the valve on top the keg, I only have about 2 pounds of pressure going into the keg from my co2 tank. Does this mean I have a bad batch?? I tasted it and it doesn't seem too off. I didn't do the carbonation, my dad it for me, and he is experienced, but I am not sure if he did something wrong. Can you initially over carbonate the beer when first putting it into the keg? I let it sit for about 2 weeks. I used sugar to carbonate the beer, I also think my dad jacked the keg full of co2 from the tank. Any idea what could be my problem??

Answer
It's easy to overcarbonate in the keg. General rule of thumb, which you probably already know, is to use 1/2 to 2/3 of the amount of sugar you would use for bottle carbonation. And once the CO2 is in the beer, it can take it a long time to diffuse out, even if you release pressure regularly. This is probably what's happening to you.

What can you do at this point? You can chill it, which will increase CO2 solubility and reduce pressure. You can use a longer dispense hose, which will drop more pressure between the keg and the faucet. When you dispense, be sure to open the tap all the way. A partially open tap creates a constriction point which will cause foaming. If the beer is coming out too fast with the tap open all the way, relieve keg pressure first.

Generally, I aim for about 10PSI going into the keg for a clean dispense. Your CO2 regulator probably has a check valve, which means that if the pressure coming out of the regulator is lower than what's already in the keg, gas (or worse, beer) won't flow backward into the regulator. But it also means that you could have the regulator set to a very low pressure and still have higher pressure inside the keg. So, release pressure in the keg until some gas is flowing through the regulator. That will ensure that the pressure in the keg is what you have set. Again, if the beer is highly carbonated, as soon as you do this, it will start gassing out and will raise the keg pressure back up. Just keep at it, and eventually you'll get to a happy place.