Tag Archives: racking

Racking From a Carboy Into a Keg Under Pressure

26 Feb

Oxidation.  Typically, that’s an unwanted effect in your finished beer.  This is true for most beers, especially in lighter style beers, but in sweeter, heavier and higher alcohol beers it can have a sherry like element that is desirable and is most prominent in old ales.  One award winning homebrew I tasted was a porter that was just old, but time and conditioning had transformed it into a beer falling squarely into the old ale style guidelines.  This is something that is achieved simply by aging the beer properly but if you crack open your latest homebrew and taste paper or cardboard, you have introduced a significant amount of oxygen into your beer post-fermentation.  One time while trying to diagnose a faulty beer over the phone, I inquired about the brewers process and he stated he “poured” the fermented beer from one bucket to the next.  That was all I needed to hear and I knew exactly what the problem was.  Read this paragraph understanding that oxidation can be good and bad, but mostly bad and it depends on how you go about getting an oxidized beer.

Lets stop for a minute and talk about the difference between oxidation and aeration.

Aeration is something that should be done to your wort pre-fermentation and before you pitch your yeast.  The act of boiling your wort has pretty much devoid it of oxygen and your yeast needs oxygen to quickly begin their job, build healthy cell walls and reproduce.  Somehow, you need to reintroduce oxygen into your wort.  This can be done by capping and shaking your fermenter or directly injecting filtered air from some kind of air pump (aquarium pumps are pretty popular for this) or filtered oxygen.  Both are best dissolved through an aeration stone into the wort.  Aeration results in shorter lag times between pitching the yeast and the first signs of fermentation.  I actually end up aerating my wort twice, once by creating a whirlpool in my kettle to isolate cold break and then once more with pure oxygen.  This could be overkill.  I’ve never had it tested in a lab but my beer turns out pretty good so I’ll keep doing it.

Oxidation occurs post-fermentation, usually due to sloppy racking and splashing the beer.  Think of oxidation as rust on metal.  This can also bring on spoilage.  Have you ever poured beer from a keg that has been dispensed from a hand pump?  The keg is being pressurized by atmospheric air.  That’s okay for a day or two, but beyond that, the beer will taste spoiled.

Therefore, transferring your beer under CO2 pressure into vessels purged of oxygen is one more way to improve the quality of your beer.

Probably the biggest downfall of this is process is the use of CO2.  Its not always cheap.  And if you only have a small 5 pound tank you know how fast you can deplete it.

Also, before you attempt this, you must understand that carboys are not designed to hold pressure.  I say again, carboys are not designed to hold pressure.   DO THIS AT YOUR OWN RISK AND TAKE ALL SAFETY PRECAUTIONS!!!  Your results may vary.  I want you to be completely aware of this because all carboys are not made the same.  Some are thicker than others, may be heavier or not be as good of quality than others.  Some are different shapes are made in Mexico, Italy and China and they all have a different process and standards in their manufacture.  This process must be done at a low rate of pounds per square inch (P.S.I.) that is set by your regulator.  (All of that can be read as “don’t sue me if something goes wrong” — you have been warned.)

First of all, the most PSI I have used is 2.  I’ve heard of people doing 3 to 5 PSI and the transfer process is faster.  I’m a little too scared to go above 2 PSI and beyond that with my system its a waste of CO2 anyway.  I’ll talk more on that later.   So know your PSI limitations before you attempt this.

The necessary equipment is as follows (aside from your normal corny keg draft dispensing equipment):

  • Racking cane with sediment tip
  • At least 3 feet of 3/8 I.D. tubing (or whatever O.D. your racking cane is)
  • Carboy cap
  • 1/4″ MFL to 1/4″ barbed fitting
  • 1/4″ FFL swivel nut to 3/8″ barbed fitting
  • Hose clamps or zip ties
  • Beverage out QD for your keg (you should already have this if you are kegging)

Note: barbed fittings may vary based on your tubing size.

Assemble the carboy cap and 1/4″ MFL to 1/4″ barbed fitting as follows:


I like a zip tie for this because I feel by having a loose connection here and by not clamping down the carboy cap onto the carboy, it sort of makes for a built in pressure relief system.  When I have this operating, I can hear pressure escaping.  Its wasted CO2 for sure, but I like it for safety reasons as well.

Next, insert your racking cane into the carboy cap.  Connect your tubing and flare fitting so you can connect to a corny keg quick disconnect.


Attach your appropriate QD and fix the entire assembly into the carboy so its ready to rack.  Purge your keg with CO2.  Do this a few times and bleed off the pressure to make sure all the air that’s in the keg has been replaced by CO2.  Fill it one last time with CO2 a little bit.  When you get ready to connect to your keg, open the pressure relief valve and turn it (or flip it for some) so it remains open.  Connect to your beverage out post on your keg.  Although this is the outlet, you will be putting the beer in through the dip tube.  By now, everything is assembled and connected and ready to add CO2 pressure.  It would be wise to have your pressure set beforehand instead of accidentally blasting it with some sort of dispensing pressure meant for kegs.  Remember, aim for 2 PSI MAX!

Your CO2 system is attached to your carboy via the carboy cap.  The racking cane is attached to your keg OUT post.  Your keg is purged with CO2 and pressure relief valve open.  You are ready to add pressure.

I still get a bit nervous pressurizing a carboy.  In reality, the really stout ones can probably take quite a bit of pressure but in the back of my mind, I’m prepared for it to shatter and spend the next hour mopping up beer off my garage floor with a gigantic glass shard protruding from my torso.  Please, please, be careful if you try this and don’t jack up the PSI unless you are prepared for a catastrophe.


(Please note, the void in the tubing is not ideal and is against what you are trying to accomplish.  I took this photo and stopped the process so the tubing was filled with beer and then transferred.)

With my CO2 system being fixed the way it is having the gas lines going through the wall of the kegerator, I’m forced to do this with the door open if I want to have gravity assist the transfer effort.  I tried that method and also having the keg level with the carboy and I didn’t notice a difference in time to rack.  So the big benefit for me is I’m able to close my kegerator and let the magic happen.  If the carboy explodes, then I will have a mess but the danger is contained.

In summary, please be careful.  I can’t stress enough that things can go wrong and you need to understand I’m in no way saying you should do this or follow my direction.  I do it and it works for me.  Your mileage may vary.  Also, understand that you are going to be wasting CO2 you will never see again.  But in all honesty, I waste 10 times more CO2 pushing cleanser and sanitizer through my draft lines.  My next project is to figure out draft line cleaning with compressed air, so at the end of the day for me, I will be ahead of the game for saving CO2.

As a homebrewer, you can achieve everything that craft breweries achieve.  You just have to think in the small scale and work within the boundaries and equipment you have.  Almost every craft brewery started in the home with people doing things like this.  And I can tell you with absolute certainty, most of the brewing innovation these days is happening in the home.  Don’t be afraid to dream big and brew small.