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Master Brewers Association of the Americas > BREWING RESOURCES > Ask the Brewmaster > Posts > Cellaring/Serving Tank Purging
February 15
Cellaring/Serving Tank Purging

​Question

We've been looking for some information on 'best practices' for preparing brew pub conditioning and serving tanks (7, 10, and 20 bbls) for receiving beer. This question is motivated by our experience of premature spoilage of our Stout and Brown ales (accelerated oxidation in melanoidin-rich environment?). I've been digging around on the BA Forum and in the MBAA Practical Handbook, but have not found anything specifically addressing how best to purge a tank with CO2.

I have had decent results over the years using the "sniff test" method of introducing CO2 through the bottom of our conditioning and serving tanks and gauging when CO2 displaces O2 by the 'sting' of the discharging gas in the nose. In spite of the subjective nature of that method, it has proven a decent, if unsafe, SOP. Now that we have three pubs staffed by three different brewers, the method is breaking down.

Are there any resources you know of that address 1) efficacy of purging from the bottom w/ CO2 and transferring fully-attenuated beer immediately/on the same day vs. letting "purged" tank stand overnight under pressure before transferring; and 2) a device that can accurately, consistently, and reliably detect gaseous O2 levels as they exit a conditioning/serving tank (in our case through the CIP arm)? Questions have arisen about to what degree o2 and CO2 mingle when purging a tank and how that might impact the life expectancy of our Brown and Stout. No doubt there are other avenues of inquiry about why beers might spoil, but we're only currently experiencing this in these two styles (and not right away upon serving = ~3 weeks after brewing).

FYI: similar methods are employed prior to moving/serving hop-centric pale ales, and we're not experiencing the same degree and/or rate of degradation.

Any insights you might be able to share would be much appreciated.

Answer

The best way to purge a tank is to fill it to overflowing with water and then press the water out with CO2 or N2 gas. The water can be pressed to another tank for other use or sent to the drain.  This will give you an anaerobic interior to the tank but the beer going in should be through a packed line. Fill your beer hoses with water until you get all the air bubbles out and then push the water out with beer before allowing it to go into the tank that way you don’t re-contaminate the tank with air.

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