Estimating Hazen-Williams Coefficient for Polyethylene Pipes

Abstract

Polyethylene is the predominant pipe material for trickle irrigation laterals and submains because of its flexibility and resistibility to the sun. Laboratory experiments have been conducted to determine the proper values of the Hazen-Williams friction coefficient for commonly used polyethylene plain pipes of different diameters. The commonly recommended values of the Hazen-Williams coefficient range from 130 to 140 regardless of the pipe diameter. Results of this investigation indicate that the average Hazen-Williams coefficients are 129, 136, 144, and 148 for pipe diameters of 13, 16, 19, and 22 mm, respectively. The differences between the measured friction losses and those calculated based on the average Hazen-Williams coefficients are small and vary from 8 to 14% at pipe diameters of 13 and 22 mm, respectively. The differences in calculating friction losses based on the commonly recommended values of the Hazen-Williams coefficient (130 to 140) and those based on the average coefficients reach 27% at a pipe diameter of 22 mm.