A pipe installed today with excellent flow capacity will not have that same capacity in thirty years — and the top-level operator who understands why, and can quantify it, is the one who can defend a capital replacement budget to a utility board with numbers instead of guesses. This guide covers the hydraulic design math behind pipe sizing and capacity — the Hazen-Williams equation and the roughness (C-factor) that drives it — and the asset management discipline that uses that understanding, plus condition and risk data, to decide which pipes get replaced first.
Pipe Hydraulics: The Hazen-Williams Equation
When water flows through a pipe, friction between the water and the pipe wall causes a loss of pressure (head) along its length. The Hazen-Williams equation is the empirical formula most widely used in water distribution engineering and operator training to relate a pipe's f