Pump Head - scale resistance

I wanted to use some old galvanized pipe to extend a supply line, and it had a lot of scale in it. I found the formula for determining scale resistance:

A * [(B + C)(D - E) - F(G*H) ] / J = I, where I = scale resistance

A = atmospheric pressure
B = Barf's constant
C = velocity coefficient
D = Daviididoff's diameter of equivalent non-scaleable pipe
E = e
F = Fahrenheit of Fluid
G = galvanized pipe length
H = free hydrogen volume
J = Jared's fudge factor

First use the engineering toolbox formula for pump head for non-scale pipe, then take that to I'th power. It really works. I put a flow meter on the extended line, and the calculated flow was within the accepted error factor of 15' of the measured pump head.