The Closed-System Page
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I spend a lot of time explaining to fellow homebrewers how to ferment in corny kegs and do closed-system transfers that I decided to take the time and add a page to my site to give some details. I hope this helps you understand how easy and efficient this is, and it can improve the quality and clarity of your beer.

Fermenting in corny kegs is a great method, better than anything else I've found including those bulky and expensive conical fermenters that look so cool, but don't give much to the homebrewer. With a corny keg you have a pressure-rated vessel that can be easily cleaned and sanitized, and which already has a transfer/racking system installed. As you see in the pictures, all you need to get is a keg, a gas disconnect, and some hose for a blowoff tube. The hose is connected to the gas-in post of the keg, and the other end of the hose is placed in a jar of your choice of water or sanitizer. The rest of the needs are already built into the keg. You leave the "liquid-out" tube in place so you can easily rack the beer later without opening the keg to the outside air. Don't waste your money on those kits for fermenting in a corny that simply adapt a connector to a standard airlock as that is just a waste of money, and you can always use the blowoff hose and disconnect for other things.

When I started fermenting in cornies, I would have the krausen from the fermentation rise up and blow out the blowoff tube. While that was what the blowoff tube was for, I don't want to lose some of the good stuff that is contained in the krausen. Cleaning the keg fermenter and blowoff tube afterwards was a real chore as well. To fix this issue and improve my process, I've started using a foam control product. It is commonly called Fermcap-S and is available from the homebrew supply shops in a little eyedopper bottle. Just add a drop per gallon and you will love fermenting in kegs! If you are trying to ferment using the full volume of the keg you will probably need 1.5 to 2 drops per gallon, but I use larger kegs to give me the headroom for some krausen to rise. I just don't want it to get on the underside of the top of the keg where it is difficult to clean, or even see.

Transfers... the best reason to use keg fermenters!

To perform a closed-system fermentation and transfer you can use any of the currently available solutions such as glass carboys, plastic "Better Bottles", some of the buckets, Vittles Vault containers, etc. If the container can tolerate a few pounds of pressure, you can start the siphon with CO2 pressure, and prevent oxidation and contamination of your brew. And no, we are not dealing with any more pressure than you can blow with your mouth, so don't think you are going to fill a glass carboy with high pressure or anything. If you design something that introduces high pressure into a glass carboy, please film it so that the paramedics know what made such a mess in your house.

As this method deals with gas and containers under pressure, you do it at you own risk, and get proper training if you are not familiar with any of the components of the systems explained here. And for my disclaimer; Like always, never, ever, under any circumstances should you ever do this yourself.

Even if you spray beer all over the wall and your significant life partner gets angry, don't blame me!

A benefit of using corny kegs as fermenters is that you don't have to worry about light skunking your beer, and you don't have to move or disturb the fermenter when transferring. If you don't have to move it or insert a racking cane, you won't disturb the sediment and yeast in the bottom.


As you see, you can ferment in any vessel that can be sanitized, won't affect the beer, and that can be sealed to keep out the beasties floating around in our atmosphere. Glass carboys are great and inexpensive, but they must be protected from the light, and when a racking cane is inserted you disturb the sediment. Plastic containers are also very good, but some buckets don't work very well for pressure transfers due to design. I have used the Vittles Vault containers as shown here with great success, and after a slight modification to the lid mounting ring it can be taken apart to sanitize the captive inner o-ring.

My preference is fermenting in large corny kegs, although any corny keg works fine. Most of the time I use 15 gallon corny kegs as shown above. These give me good headroom for fermenting my 10 gallon batches. I also use 10 and 5 gallon models depending on batch size.

I always use foam control drops (Fermcap-S) to reduce krausen that will get up into the blowoff tubes and just make a mess. Also there is talk from many of the experts (which I'm not) that the krausen loss from a huge blowoff can affect the quality of the beer. I've found that using half of the sugested 2-drops per gallon is more than enough to make the krausen manageable. Remember that the goal is to keep the krausen out of the blowoff tubes, not eliminate it completely. It also keeps the gunk on the sides of the keg limited to a band a few inches wide, so cleaning is easier than trying to make sure you get all the gunk from the inside top of the keg where it might be difficult to detect. Foam control drops are available at More Beer, Northern Brewer, and most better brewing supply stores.

The Hardware
We can break this down into two different categories. The first is simply a siphon-starter with CO2 pressure where the siphon principle takes over, and the CO2 is simply there to replace the headspace in the vessel.

The other is actually a transfer under pressure where the pressure remains the driving force. This is true where your vessels may be at the same level and siphoning is simply not workable.

I suggest that you only use constant pressure to transfer where you are using a pressure-rated vessel such as a corny keg.

The device shown to the left is a rubber plug that was drilled to accomodate a stainless racking cane, and a small barb to 1/4" flare fitting. Then a 1/4" male flare (MFL) to 1/4" male flare elbow was installed to allow the easy connection of the CO2 hose.

The rubber stopper will pop out of the carboy or other vessel before any amount of pressure builds up. I don't suggest jamming this stopper down very tight as the ability to pop out under high pressure is a benefit, not a problem.

1/4" flare fittings are the best method for assembling any air pressure or beer system. Barbed fittings should be avoided due to the difficulty of taking the assembly apart for cleaning or reconfiguration. Making all my hoses with these fittings allows me to use any hose on any part of my setup from serving beer to carrying CO2. I just change the disconnects. Shown are the little washers that help when you are making a metal-to-metal connection. The corny keg disconnects shown below have built-in washers and do not require these little parts.

Northern Brewer parts K123, K163, and K127 for the washers.

Use good beverage-grade hose so I don't have to hear you whine about problems with flavor, or foaming, or anything else. Cheap vinyl hose from the local home improvement store may work in a pinch, but it isn't worth the savings. The fiber-reinforced hose they sell is fine if they have the proper sizes, but that is rare, and beverage-grade hose is usually cheaper anyway. I use 3/16" ID thick-walled beverage lines as a standard hose. I also use 5/16" ID of the same for CO2 only, but the CO2 part is not critical to size, and most of my lines are 3/16" because I bought a lot of it at one time :-)
Get the 1/4" flare (MFL) disconnects (shown in front) and use the fittings shown above to connect them to the tubing. The barbed versions are a PITA to clean and cannot be reconfigured easily, so they are useless in my opinion. You will spend a few more bucks making the lines up with flare fittings, but you will thank me later.
Worm-gear hardware store hose clamps just stink. These are Oetiker brand stainless steel stepless pinch-free ear clamps. They will not deform or cut into the hose. Although they need a tool to install, any nail-cutter type tool works well and will be under $10 at places like Harbor Freight.
Spend the extra $5 and get the premium regulator with the large handwheel on the front for adjustment. This doesn't require tools to adjust pressure.
It doesn't matter if you buy a steel tank or a shiny new aluminum unit, but make sure before you buy one that you can get it filled locally. If you only have a gas provider who does exchanges it is usually best to pay their price and start the exchange program. A bigger tank will allow you to go longer between fills if you live farther from the gas provider. Some folks prefer two smaller tanks so they always have a full backup. I have a 10lb for the kegerator, and a 5lb for a backup and for the transfers. The only reason I bought these sizes was that they fit my kegerators at the time.
Hook Up the System
Now it's time to hook up the system and move some beer. I'll try to go step by step and not leave out the small details.

Step 1: Clean and sanitize a keg. If you ask me I'm going to tell you to take apart every single component of the keg and system to clean and sanitize it. I don't care if you did it last week, I'm going to tell you to do it again, so just get to it. I use PBW or OxyClean for cleaning, and Star-San and Sani-Clean as my sanitizers. These are no-rinse, and the leftover foam from Star-San will not affect your beer, so don't worry about it.

There is a reason that sanitation is important here. All homebrew contains some sort of bacteria and contamination. How well you sanitize will be reflected in the long-term deliciousness of your brew. Most people never know they are drinking contaminated homebrew because it doesn't last long enough for it to be discovered. For those folks who keep kegs around for more than a few months, sanitation is a key quality factor. The only part that might be difficult to remove is the poppets in the posts, so if you can't pop them out easily, just give them a good soak in the cleaner and sanitizer, and blow them out with air if possible.

Step 2: Connect the CO2 line to your RECEIVING keg and fill your keg with a few psi of CO2. Pull the pressure release a few times to let the oxygen escape. Make sure that you do not leave any pressure in this receiving keg because if you do, you'll get a backflow when you connect the transfer lines and it will disturb the sediment in your fermenting vessel. Then you will want to wait for the debris to settle once again before racking. Leave the pressure relief valve open on the receiving keg. Nothing will get in there in the next few minutes.

Now disconnect the CO2 from the RECEIVING keg. Turn off the valve between the regulator and your CO2 line to the keg connector. Turn the pressure on the regulator down so that the needle drops down as close to nothing as possible while still registering. Make sure there is no pressure left in the line by pressing into the disconnect to purge it. We do this so we don't start the siphon as soon we we connect the line to the fermenter.

Step 3: Connect the transfer hose to your fermenter or fermentation keg (sending keg or container). You will connect the transfer hose to the receiving keg's LIQUID OUT with a LIQUID OUT (black) disconnect, but leave that off for the moment as we will use this end to allow the debris and the first few ounces to dump into a container before actually connecting the hose to the keg.

Step 4: Connect the CO2 hose to the fermenter. Your setup will vary here, but there should not be any pressure in the CO2 line at this time.

Step 5: The fun starts. Open the valve between the regulator and the CO2 line to the fermenter. You should have the regulator set as low as possible so that CO2 might not even be flowing at this time. SLOWLY tighten down the regulator pressure knob until you hear some CO2 flow. DO NOT increase the pressure, and you might not even see this CO2 flow register as pressure on the regulator gauge at this time, so don't worry. As the pressure builds in the vessel, the flow will start. Don't rush this by increasing the pressure, especially if you are using a carboy or the top will pop off. Have the hose to the receiving keg placed into a sanitized container to catch the first few ounces of junk that will come out.

Step 6: The flow starts. This is a tricky time as we want to let the trub, debris, yeast, etc in the first few ounces to drop into a container to be disposed of, or used for a hydrometer sample. I told you to leave the hose off the receiving keg for this reason. I usually get a cup of liquid before I connect the hose to the keg connector. As we are using virtually no pressure, once we have the debris clear, we can raise the hose up high enough to stop the flow momentarily and connect the keg connector to the hose. This is why I tell you to use the threaded flare connectors and not barbed connections. Once the connector is connected to the hose, it stops the flow until you connect it to the keg.

Step 7: Connect the hose and disconnect to the receiving keg's LIQUID OUT connector. Make sure the pressure relief valve in the receiving keg is open to allow the liquid to purge the contents of the keg as it rises. Don't worry, nothing can get into the keg as the air flow is outgoing. Some folks including me have used a blowoff tube on the receiving keg, but that is not required.

Step 8: Only if you are using a pressure-rated vessel (keg) as a fermenter, you can increase the CO2 pressure slightly to increase the flow. You still might not see the pressure register on the CO2 regulator, but once you hear the CO2 flowing through the regulator, that is all you need.

Step 9: Watch closely because when the fermenter is empty you will need to snatch the connector from the receiving keg to prevent the last bit of beer that will contain yeast and sludge from getting into your keg. Once you are done with the transfer, clean up the outside of the receiving keg, hit it with about 20psi of CO2 to make certain that is seals and check for leaks. After that it is ready to be set aside for aging, or to be placed into the kegerator for serving.

When racking from a non pressure-rated vessel such as a carboy, you can leave the CO2 flowing slightly to replace the volume of liquid that is leaving, and prevent any oxygen from getting into the vessel. And again, don't try and rush the transfer from a carboy by adding pressure as you will only blow the plug out of the carboy and mess up the process. If the plug happens to stick you could possibly explode the carboy and send shattered glass everywhere. Hopefully you won't need a trip to the emergency room to make you use some common sense. I've never seen or heard about a carboy that ruptured from pressure transfer of beer, but I'm sure someone will invent something that make it possible.

Another tip: Place your receiving kegs on a bathroom scale so you know when they are full without having to open the top of the keg. A full 5 gallon keg will weight 50lbs filled to the bottom of the "in" diptube.

Here is a photo of the CO2 line connected to the racking cane stopper shown previously. This is shown as installed on a Vittles Vault container. With this method you only need a single hole for your airlock/blowoff tube, and your racking system.
Here is a wider view of the racking cane and pressure stopper installed on a carboy.
If your beer is ready to serve, you'll want to chill it and carbonate it the easy way. No reason to add priming sugar to kegs, you just need to hook the CO2 and let it carbonate. If you want to do it quickly you can shake it to allow the beer to absorb the CO2 quicker. The results are the same either way. Rather than me writing my own, here is an excellent FAQ from

Here is a #7 stopper drilled twice, once for the stainless racking cane, and a smaller hole where I used a 1/4" barb to a flare fitting. The CO2 lines from my CO2 regulators all have female flare fittings , so I just remove a keg disconnect and screw the fitting on to this connection and start the siphon. Very easy, very clean, and the beer doesn't get exposed to anything but CO2. I don't suggest that you do this because overpressurizing a glass carboy can be dangerous and maybe deadly. The stopper is loosely inserted, and no more pressure is used than if you were to blow into it with your mouth.