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

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

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)

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.