Ask Mr. Wizard

Cleaning a soda keg


Rich Kragness • Pittsburgh, Pennsylvania asks,

I recently made a 10-gallon batch of Pilsner and bottled it in two five-gallon Cornelius kegs. I used the triple decoction technique and it tasted great, at least the first keg. I had previously used the second keg for making birch (or root) beer, so the beer in that keg has a hint of birch beer flavor. This is definitely not desirable for a traditional Pilsner. What can I do to improve this batch? I can drink it, but it is not suitable for guests! The more important question is, how do I get the birch beer flavor out of my keg? I have soaked it for 20 minutes with dilute bleach (yes, I know bleach is a no-no) and for 10 days with dilute TSP. I can still smell it. What do you suggest?


Ah, the old birch-beer beer. This reminds me of a time when I screwed up a beer experiment with the remnants of a root beer experiment. We had three groups in our brewing lab class and each group would brew a beer that had one ingredient or process step changed. The results were assessed both analytically and with sensory evaluation. So, as we tasted the beer from my group, my colleagues began focusing on the odd aroma from the beer. In the end I had to confess that I had tainted the beer keg with root beer!

Unfortunately, when beer is tainted with a flavor like root beer, there is nothing that can be done to rescue it. However, several measures can be taken to ensure that the problem will not reoccur.

I learned a lesson because I tried everything imaginable to free the rubber gaskets and o-rings from the pungent odor. I soaked them in bleach, sodium hydroxide and acid. I boiled them, steamed them and even let them bake in the hot sun. Nothing worked. Finally, I spent a few bucks and replaced all the rubber parts of the keg and the keg no longer reeked of eau de root.

I love root beer and have been serving it to customers for the last five years, but I take a few precautions. For starters, I have a complete set of rubber and plastic components (gaskets, measuring cups, hoses, etc.) that are used only for root beer. I also have kegs that are only used for root beer.

The next precaution is Draconian: The root beer keg is tapped in a stand-alone keg cooler. The reason for not running root beer lines in the same bundle of lines carrying beer is that root beer flavors can actually migrate out of the root beer line and into adjacent beer lines. This seems unbelievable, but it can and does happen. There are special beer lines on the market that are designed to prevent this from occurring, but I don’t want to take any chances.

Breweries are not the only places that quarantine root beer. Soda bottlers do the same thing to prevent everything they produce from having that birch root, wintergreen, star anise, licorice and vanilla zip that’s known as root beer.

Response by Ashton Lewis.