Say Goodbye to Foamy Pours: Fixing Over-Carbonated Kegs

In our previous blog post we ran through some different methods of force carbonating your beer, where some of the methods involve a risk of over-carbonating the beer inside. If you've ever poured a beer and ended up with a glass full of foam, it's quite possible the cause is over carbonation. Here's a guide you can use to correct this if it happens to you.

Understanding Carbonation

Carbonation is the amount of carbon dioxide gas (CO2) that has been dissolved into your finished beer that gives it the required fizz and a touch of sharpness known as carbonic bite. It is measured in volumes of CO2, and is dependent on temperature and pressure.

Calculating Carbonation Levels

A carbonation chart should be used to determine what level of carbonation you currently have, or should have, depending on the style of beer you are carbonating. We have included one below from our friends at Keg King.

A carbonation chart should be used to calculate carbonation level

Looking at the carbonation chart above, if we wanted to have 2.4 volumes of CO2, and our beer was stored at 4°C, we would set our CO2 gas regulator to 11.2 psi.

You can work backwards using this same chart as well. If you have a keg stored at the same temperature (4°C) and has 25 psi of pressure in the keg headspace, then it has around 3.7 volumes of CO2 which would be considered over carbonated for most beer styles.

Steps to Fix an Over Carbonated Keg

1. Disconnect the gas line from the keg.
2. Purge the headspace in the keg by pulling the pressure release valve (PRV). Hold the PRV open until all the gas has been released.
   
   

   

   Disconnect the gas and pull the PRV to release all the gas in the headspace of the keg

3. Leave the keg disconnected from the gas for 3 hours. Some gas will naturally come out of solution to fill the headspace of the keg. The process can be sped up by leaving the keg out of the fridge so the temperature of the beer increases. As the beer becomes warmer, more CO2 will come out of solution.
4. After 3 hours, purge the headspace of the keg again by pulling the PRV.
5. Set the keg to your desired serving pressure, typically 10-12psi. You can refer to the carbonation chart at the top of this post to help determine what pressure you should set.
6. Test pouring a beer (be sure to chill the keg to serving temperature again if you let it warm up).
7. If necessary, repeat Steps 2-6.

Conclusion

There's lots of variables at play here, so patience is certainly key to getting this right. Keep in mind that releasing the gas from the keg will cause the beer inside to become disturbed and will pour as nothing but foam regardless of whether it's still over carbonated or not. This is why you need to leave it for several hours to settle before trying again.

It's not a bad idea to leave it for as long as 24 hours for things to settle down inside the keg, and for the temperature and pressure to normalise.

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