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When I started kegging, one of the first things I wondered was, “What kind of line do I need for my kegerator?” Here are some of the options:
- 3/16″ ID vinyl tubing = 3 PSI/ft
- 1/4″ ID vinyl tubing = 0.85 psi/ft
- 3/16″ ID Polyethylene tubing = 2.2 psi/ft
- 1/4″ ID Polyethylene tubing = 0.5 psi/ft
Generally, plastic tube of smaller than 3/16″ ID is not recommended as it provides too much resistance for practical use!
1/4″ ID PVC tubing that most of us use has a pressure drop of about 1 psi/ft means that an average draft system that uses 4 feet of PVC line will have about 4 psi volumes of gas pressure (about medium carbonation), this would amount to about 12 psi on your regulator at 40 degrees F (4 degrees C); 12 psi at 40 degrees F = 2.5 volumes (1). If you now subtract the 4-psi drop in line resistance, your beer is being dispensed at 8 psi, which will make for great head and no gas in your hand-crafted product.
There is a solution to this paradox. If you use 3/16″ ID PVC line, which has a pressure drop of 3 PSI/ft, you can get a 12-psi pressure drop across the liquid line. Now you can dispense your beer and maintain it at 12 psi, and by using a 4-foot liquid line (3 psi x 4 ft = 12) you will get close to a 0-psi pressure at the tap. I switched all of my draft lines to 4 feet of 3/16-inch ID PVC line and now maintain and dispense all my beers at about 12 psi. I have never been happier with my draft system!