Keg Line Length Balancing

Here's a great article found at http://www.beersmith.com/blog/2011/07/14/keg-line-length-balancing-the-science-of-draft-beer/

Keg Line Length Balancing – The Science of Draft Beer
...
So how does one design a draft beer system to maintain proper balance at the tap? The pressure drop depends on resistance in the beer line. Beer lines have two types of resistance – one due to elevation change (i.e. the keg being higher or lower than the tap), and a second due to the beer lines themselves which generate friction as the beer flows through the lines.

Lets look at resistance first to keep things simple. Here are some sample resistance ratings for various popular beer lines:

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
3/8″ OD Stainless tubing = 0.2 psi/ft
5/16″ OD Stainless tubing = 0.5 psi/ft
1/4″ OD Stainless tubing = 2 psi/ft