Homebrewers, strangely, have made a mystery of kegging. In this first practical post of the Brewing section of the Beer Simple blog, we're going to simplify kegging and draft service for you - and I'm not just talking about for newbies. I know a great many brewers who insist on making their keg systems work way harder than they should, so even if you already keg regularly, read on and see if there's anything you can use.
The appeal of kegging should be obvious: cleaning and sanitizing bottles sucks, and the more you brew (both in frequency and in volume), the more it sucks. Kegging is the go-to answer. No bottles to clean and sanitize! No priming sugar to mess with! One transfer and WHOOSH: great beer on demand. And in truth, it really is that simple (or at least it can be). All you need to do is a small amount of math up front to balance your system, and then LEAVE. IT. ALONE. As in so much else to do with beer, balance is the name of the game.
A lot of brewers only pay attention to the pressure needed to create the volumes of CO2 they want in their beer, at a certain temperature. Anyone who has spent any time kegging has seen this table (or something like it):
Tables like this give you an idea of what to set the CO2 regulator at, given a certain target for carbonation and a certain temperature Fahrenheit. This, though, is really only two-thirds of the story.
Once you carbonate, that beer, you need to serve it, and this is where balancing comes in. You want a smooth, steady, and easy pour out of the faucet, otherwise you'll end up with a glass full of head, spilled beer, beers that take three minutes to pour, a distinct lack of enjoyment, or maybe all of these.
A BALANCED SYSTEM is one where the applied pressure (CO2 on the beer) creates the desired level of carbonation (per the table above) is equal to the resistance created by getting the beer to the faucet. Resistance can be caused by changes in elevation (pumping up from a basement, perhaps), but is usually caused by the tubing between the keg and the faucet. Once you know your temperature and your desired carbonation level, all that remains is the create (or eliminate) the appropriate level of resistance, and you're all set! Once your system is balanced, carbonation and service is as simple as 1.) Connect keg, 2.) Wait.
A common mistake that I've helped at least a dozen folks correct over the years is trying to fix everything by adjusting the regulator. Too splashy? Turn it down. Too slow? Turn it up. And it never, never ends... That's the mistake. Once you decide on a CO2 level and a serving temperature, you should never touch the regulator or temperature controller again. Do this right the first time, and all of your dreams will come true. No, wait, that's not right - but you definitely won't need to mess with your kegerator, regulator, or tubing again, and you'll pour perfect beer every time.
So, how do you work out resistance and create balance? Easy.
Let's start with a typical case. You have a converted chest freezer on a temp controller with a few taps coming through a wood collar or the top of the freezer lid. Your kegs are just inside. You decide that you want your beers served at less-than-cellar-temp-even-though-it's-better-at-55F-because-otherwise-people-will-complain (or, more briefly, 40F), and you want a good all-purpose level of carbonation because (if you're reading this blog) you want your beer life to be simpler, so you go with 2.2 volumes of CO2. We consult our handy table above, and see that we need to set the regulator to 9.1 PSI to create and maintain that level of CO2. We do so, connect our keg, and we're done - except that the beer is pouring WAY too fast and creating mugs full of head, or it's coming out at a trickle.
If we reduce the CO2, the pour rate slows, but we're also slowly de-carbonating the beer in the keg. If we increase, the pour rate picks up, but the beer itself is a carbonic, bitey mess. The fix is in the amount of resistance.
In almost every case of this type, the tendency is that the beer is pouring way too hard. That's because your run of tubing is too short to provide the resistance needed to slow it down at 9.1 PSI. The answer is simple: measure and cut a new tubing connection for the PSI level you've chosen.
Most of us use 3/16" ID vinyl tubing to connect to our kegs to our faucets. 3/16" ID tubing creates resistance equal to about 3 pounds per linear foot. To balance our hypothetical system (running at 9.1 PSI), then, we need 36.4 inches of tubing between our keg and our faucet connection to create a balanced system (36.4" x 3 lbs/ft = 9.1 pounds of resistance). Go to the LHBS, cut a piece a little longer than you need, take it home and trim to the just-right length, and connect via hose barbs. You're done!
Height matters, too, but in most systems the height difference is negligible. You don't need to worry about that few inches of rise from the top of your keg to the height of the faucet, but if you're a stickler, you should know that you're getting 0.43lbs of resistance per foot of rise. You can factor that in if you want. Elevation affects this, too, so consult an authoritative source if you're more than a couple of hundred feet above sea level.
So, to recap:
1. Decide on a level of carbonation (volumes of CO2) and serving temperature that will work for most of the beers you make/serve.
2. Consult the PSI/temp table to determine the PSI level on the regulator.
3. Calculate the amount of resistance needed to balance the system as a function of how much resistance you get from your connection tubing and any height differences (3 lbs/ft for 3/16" ID, 0.43 lbs/ft in height adjustment if the tap is above the keg).
4. Procure, cut, and secure the proper length of tubing.
And that's it! Now, any time you have a new keg ready to go on, just connect and forget it. In 2-3 days it will be properly carbonated, and you can trust even your most clumsy and/or tipsy friends to pour for themselves.
Time for a just a couple of caveats:
1. This will mean that ALL of your beers will be at the same temperature and pressure, so you're serving a Berliner Weisse at the same pressure as a Standard Bitter, even though you'd expect three times the CO2 in the sour. That's true, but it's also a pretty minor point. Most beers are perfectly enjoyable at about 2.2 volumes, but if you're really committed, you can use independent regulators to create different pressure situations on different taps: just remember to cut different lengths of tubing to balance each tap, and note which are your "high CO2" and "low CO2" lines.
2. You won't have a new keg ready to go on demand - it'll take a few days (three is about right for me) before the flat keg's beer is properly carbonated. If that concerns you, you can always pre-carbonate your kegs using a second cylinder and regulator - hit it with 30 PSI for a 4-5 hours, then disconnect it and set it aside for storage. When you do ultimately attach it to your serving cylinder/faucet, be sure to bleed it to get rid of that first possibly-over-pressurized spurt (hold a mug under the tap and whip that puppy open), and you should be ready to serve almost immediately (or if it is a tad under-carbonated, no one is likely to notice).
So that's draft system balance made easy - set it and forget it. These same rules apply whether you're connecting to a ten-tap system or a simple cobra/picnic tap: you should always be starting with volumes of CO2, and then balancing from there. It keeps it simple, which is, around here, the point.
Be sure to check out the BA Draught Beer Quality Manual (http://www.draughtquality.org/wp-content/uploads/2012/01/DQM_Full_Final.pdf) to determine the resistance levels for your specific equipment/tubing, and when in doubt, consult your nearest Certified Cicerone (R), as draft system balance is an essential part of their certification!