Closed Transfer Kegging
08/16/2023
By Aaron Deboer
If you are like me, you are always looking for ways to make better beer by using new yeast strains, new hops, better equipment, and better processes and procedures. In this article, we will cover a process that can help kegged beer fresher for longer. It may also inspire you to make some equipment upgrades or think of creative ways to use what you currently have.
This article covers closed transfer kegging, which is the process of moving beer from a fermenter to a keg while both the keg and the fermenter are closed, limiting oxygen ingress and keeping the beer as fresh as possible.
We should always work to reduce oxygen exposure of our finished beer to retain all the flavor and aroma we worked so hard to build during the brew day and fermentation. Oxygen exposure will lead to oxidation which can make a caramelly beer taste overly sweet, hops taste green and catty, and dark beers taste like sherry or soy sauce. Oxidation in beer will also produce papery, leathery, earthy, and musty flavors that are unpleasant and out of style. Oxidation during packaging is often the cause of your beer tasting great at home, but then only scoring a 24 in your local homebrew competition.
Closed transfer kegging works by transferring beer out of a port or valve on the fermenter and moving it into the keg via tubing connected to the liquid post and a quick disconnect fitting. At no point is the beer exposed to atmospheric oxygen. CO2 is used to create positive pressure on the fermenter side, blanket the beer, and force the beer into the keg.
At a minimum, this procedure requires a keg, a CO2 tank setup, tubing/quick disconnects, and a fermentation vessel that can hold at least 2 psi of pressure, so buckets and carboys are out. Additionally, a spunding valve and a scale are useful, depending on your specific transfer setup.
Regardless of your equipment, there are some crucial first steps that may not be obvious. You need to purge all of your lines and vessels. Your fermentation vessel is likely ready to go, it has been making CO2 for the last 5-10 days as part of fermentation is already purged. Your gas line can be purged by depressing the poppet and letting some gas run through. Your beer line can be purged by letting beer run out at the end of the tube until the tubing is full of beer. Now we need to purge the keg, this can be done by filling the keg with liquid sanitizer and pushing the sanitizer out with CO2 into a bucket. You can use that sanitizer for any other transfer-day sanitization purposes.
There is another way to purge a keg that conserves CO2 and sanitizer. Your fermenting beer produces a significant amount of CO2 which is more than enough to purge a 5-gallon keg. A 1.045 beer at 65% attenuation produces 10 Cu Ft of CO2.
This setup begins with sanitizing your keg with 1-2 gallons of sanitizer, empting the keg and connecting it to your fermenter. The gas output of your fermenter is connected to the liquid- out post of your keg and a blow-off tube or spunding valve on the gas-in post. Below is a picture of a fermenter and keg setup to purge for an upcoming closed transfer. You can see this setupis using tubing and a spunding valve. This is a great way to use the excess CO2 produced by your beer that would normally disappear into the atmosphere. It can also help to reduce your transfer day tasks as you have a sanitized and purged keg ready to go. Note: disconnect your keg from the fermenter beginning any cold crash or temperature drop.
Now that we have a purged keg, purged tubing, and a beer ready to transfer, let's take a look at some real-world examples of this process being used to transfer the beer.
In this first example, you can see CO2 being used to push the beer out of the fermenter's racking port, through a piece of tubing to a liquid post disconnect on the keg. A spunding valve is connected to the gas post to release the displaced gas from the keg. I am also using a scale here to weigh the keg and the beer to know when I have 5 gallons of beer in the keg.
You don't need an $800 conical fermenter to perform a closed transfer. In this second example, you see a Delta fermenter being used. The fermenter is pressurized to 2psi, the keg is pressurized at 1 psi or lower, and the output of the keg is connected to the top of the fermenter. This is a closed-loop transfer, the gas displaced from the keg goes into the fermenter to replace the space of the moving beer. Gravity is important to create a siphoning effect as well so ensure that the fermenter is higher than the keg.
Photo by Nick McLawhorn
In this last example, you see a Fermzilla fermenter being used in a similar way to the conical. The Fermzilla has a floating dip tube connected through the top bulkhead by a ball lock post, the ball lock connector is connected to the keg’s liquid out with another ball lock connection. The keg has a spunding valve on the gas post and CO2 from a tank is pushed into the fermenter to transfer the beer into the keg.
Photo by Rod Templen
As you can see, any closed transfer system will have similarities in that they use pressure and tubing to ensure the beer is never open to the atmosphere at any point but are customized to the fermenter the beer is being transferred from.
We can never completely eliminate oxygen, but taking care to limit oxygen exposure during transferring finished beer into the keg will ensure your beer smells and tastes the best it can be for the longest time possible.
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