ABSTRACT
This chapter considers friction head loss in closed pipe systems. The work is straightforward once the components are understood and inherent weaknesses in theoretical calculation are overcome by adaptation to each particular water system. In a dynamic system, pressure decreases along the length of the pipeline; the Hydraulic Grade Line slopes downward, designating pressure loss from friction created as the water encounters the sides of the pipe. Friction losses occur with every foot of pipe length, and this must be included in head loss calculations. Normal flow in water pipes is turbulent, and that turbulence increases with pipe roughness; energy is spent, and pressure drops over length. In a large diameter pipe, less of the water is actually touching the sides of the pipe and encountering friction, than in a small diameter pipe. With the Hazen-Williams formula came a new designation of pipe roughness.
