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Getting A Good Pour – Kegged Beer CO2 Line Length and Pressure

Saturday, July 18th, 2009

There are several variables that play a role in achieving this goal, AND you will need a calculator!

Factors that play a role in the quality of your pour are the following:

Beer Temperature: This will affect how readily the beer absorbs CO2. Colder beer absorbs CO2 into solution more readily. The lower the temp. the lower the pressure required to obtain a given number of volumes of CO2.

Keg Pressure: Along with beer temperature, this will control the actual volumes of CO2 in solution.

Beer Line Inside Diameter: This provides resistance, keeping CO2 in solution by slowing the pour.

Beer Line Temperature: Warm beer lines will warm the beer as it travels from the keg to your glass, causing a release of CO2.

Beer Line Length: This provides resistance, keeping CO2 in solution by slowing the pour.

Beer Line Rise to Tap: The height of the tap from the center of the keg. This provides resistance, keeping CO2 in solution by slowing the pour.

There are some simple rules to follow as well as an equation to help you balance your beer line length to accommodate the pressure needed in the keg to sustain your desired CO2 volume.

  1. Keep your beer lines cold. For some this is not an issue, but if you use a draft tower you need to take care to refrigerate those lines and insulate the tower to keep CO2 release to a minimum, thus reducing foam in the glass.
  2. Beer line length MUST be balanced with the amount of pressure in the keg used for serving. The longer the line, the more resistance you have.
  3. Beer line inside diameter MUST be included in the beer line length calculations to properly determine length. The narrower the line, the more resistance you have.
  4. Beer line RISE from the keg to the tap MUST also be included in the beer line length calculations to properly determine length. The greater the rise, the more resistance you will have.

Numbers 2-3 all work together to provide a total amount of resistance between the keg and your glass. Too much resistance and you will have a slow pour, too little resistance and you will have nothing but foam in your glass.

Here is an example of how to determine the proper temperature, pressure and beer line length for a given scenario.

BEER STYLE CARBONATION GUIDE

British Style Ales 1.5 – 2.0 volumes
Belgian Ales 1.5 – 2.4 volumes
American Ales and Lager 2.2 – 2.7 volumes
Fruit Lambic 3.0 – 4.5 volumes
Porter, Stout 1.7 – 2.3 volumes
European Lagers 2.2 – 2.7 volumes
Lambic 2.4 – 2.8 volumes
German Wheat Beer 3.3 – 4.5 volumes

Beer Temperature: 38F

Keg Pressure: 21.7 PSI

Volumes of CO2: 3.50

Beer Line ID: 3/16” inside diameter plastic beer line

Beer Line Temperature: COLD (ideal)

Beer Line length: 6′

Beer Line Rise to Tap: 24”

Beer Line Length Formula:

L = (P -(H x .5) – 1 ) / R

Where:
L = length of beer line in feet
P = pressure set of regulator
H = total height from center of keg to faucet in feet
R = resistance of the line from the following table
1 = residual pressure remaining at faucet (this can be increased to 2 if you need to increase pressure to increase dispense rate)

Line Type: Resistance:
3/8” OD stainless beverage tubing .2
5/16” OD stainless beverage tubing .5
1/4” OD stainless beverage tubing 2
3/8” ID plastic beer line .11
5/16” ID plastic beer line .17
1/4” ID plastic beer line .7
3/16” ID plastic beer line 2.7

L = ( 21.7-(2 x .5)-1 ) / 2.7

L = 7.3 feet of beer line, or 7′ 4”

In this scenario the beer line length is too short, ideally one would have over 7′ of beer line to create enough resistance to counter the 21.7 PSI in the keg to obtain the volumes of CO2 for this German wheat beer. If you simply reduce the temperature of the beer to 33F and reduce the pressure to 18.3 PSI you will still achieve 3.50 volumes of CO2 in your beer, but the reduction in pressure will now not overwhelm the 6′ beer line that you have. Pressure and resistance are now balanced.

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  1. 28 Responses to “Getting A Good Pour – Kegged Beer CO2 Line Length and Pressure”

  2. The priming sugar guide/calculator at TastyBrew.com is pretty good for this stuff:
    http://www.tastybrew.com/calculators/priming.html

    By Ethan John on Jul 19, 2009

  3. I was wondering if there is a different formula for the CO2/Nitrogen beer gas mix?

    By JD on Jul 16, 2010

  4. It is called ‘beer gas’ (mix of CO2 and Nitrogen), and it can be used to optimize a tap based on line length.

    The topic looks pretty complicated but I found this write up:
    http://www.brewboard.com/index.php?showtopic=48144

    By Larry on Jul 17, 2010

  5. This is a great explanation. I own a draft beer company (Kegconnection.com) and we are constantly get people asking us for 10′ of our 3/16 beer line on their systems. I always tell them this is way to much for someone serving beer at 10 to 12 PSI. They read on websites that if they are getting foam they should have more beer line. After working with them we almost always find that they have plenty of beer line, but their beer is too warm. I will be sending people to this link in the future. This is a very simple and easy to understand explaination.
    Thanks! Todd

    By Todd Burns on Aug 26, 2010

  6. I think there is a typo in this equation:
    L = P( -(H x .5) – 1 ) / R

    I think it is supposed to be:

    L = (P -(H x .5) – 1 ) / R

    By -TH- on Feb 17, 2011

  7. Thank you TH, corrected the post.

    By Larry on Feb 19, 2011

  8. I have German Pilsner at 34′F, charged at 10 psi to give 2.58 volumes.My dispensing line is 3/8.

    If L = (10 – (2 x .5) – 1) / .11, do I need 72 feet of tubing?!

    By jeff on Nov 13, 2011

  9. Jeff,
    That seems nuts. Something must be off with this.

    I will measure the size of my beer line ID/OD and tell you what it is. 3/8 sounds common enough. If it is 3/16, that changes the final number to 3 feet, which sounds more realistic.

    I have my regulator set at 6psi, and while it takes a little extra time to force carbonate, I get good pours through my 3 ft picnic tap without a lot of foam. I still can’t fill a pint glass perfectly, probably get 4 oz of foam and 12 oz of beer.

    Sounds like you might need a beer line with a smaller inside diameter?

    By Larry on Nov 13, 2011

  10. I have some 1/4″ ID line that I had been using with a Pepsi “gun”-type dispenser. The chilling plate and gun for the dispenser had narrower line, so the resistance was considerable.

    I have abandoned this in favour of a simple picnic tap, but the tap fitting is too big for the 1/4″ line. I was going to buy some 3/8 today and hook it up.

    I can skip the formula for now and start with 10′ of line. I’ll cut the line down shorter (if I can) to get the right pour.

    By jeff on Nov 14, 2011

  11. Turns out the tap is for 5/16″.

    By jeff on Nov 15, 2011

  12. The inside diameter of my beer line is 1/4″.

    By Larry on Nov 26, 2011

  13. How are you getting 21.7psi from 3.5 volumes of CO2. Is there an equation for this as well? Also, I understand that lower temperature allows CO2 to absorb but is there some math behind this as well? I am new to kegging and trying to get the pour just right. Thanks for this site. Between this and Designing Great Beers I have had a lot of fun coming up with my own recipes.

    By jjackson on Dec 27, 2011

  14. The missing piece of the puzzle is a temperature vs pressure chart that tells volumes of CO2. Given the pressure setting of the regulator and the temperature of the kegerator ‘Volumes of CO2′ can be found on the chart.

    This site has a good chart:
    http://www.kegerators.com/carbonation-table.php

    In case anybody wants to know, here is the simple solution I figured out that saves headache:
    1. Set regulator to 10 psi.
    2. Set kegerator to 36 degrees.
    3. This gives approximately 2.4 Volumes of CO2. In the sweet spot for most beers!
    4. 3 ft picnic tap.
    5. I can fill a pint glass almost full, with about a half inch of head, if I pour onto the side of the glass to avoid splashing, instead of straight in.
    6. Nicely carbonated beer results. No excessive foaming. There is a nice lacing of head/foam that travles down the glass as I drink, and a pattern of bubbles to look at.

    According to the equation above, I might need as much as 11 feet of line. Perhaps with 11 feet that last half inch of head/foam would disappear? If I was setting up a draft system on a professional level I might try a longer line and see how it behaves.

    By Larry on Dec 28, 2011

  15. I have 25′ of glycol trunk line with a 5/16 ID product line. I run that to my kegerator and reduce it to 3/16 ID for 3′. I have pressure set between 12-14 PSI and system runs perfect. According to the calculator I should have 50ish feet of 5/16, but I think the 3′ of 3/16 I put in the kegerator works at balancing.

    By Shaun on Nov 16, 2012

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