The ratio of frictional factor and coefficient of friction used in general equation for a head loss in a pipe, is

Determining the pipe diameter when the pipe length and flow rate are given for a specified pressure drop. hf = f L d v2 2g = 0,0225 500 0.2 6,42 2·9,81 = 117 m For inclined pipe the head loss is hf = ∆p ρg +z1 −z2 = ∆p ρg +Lsin10o.