Equivalent Pipes

Equivalent pipe is a method of reducing a combination of pipes into a simple pipe system for easier analysis of a pipe network, such as a water distribution system. An equivalent pipe is an imaginary pipe in which the head loss and discharge are equivalent to the head loss and discharge for the real pipe system. There are three main properties of a pipe: diameter, length, and roughness. As the coefficient of roughness, C, decreases the roughness of the pipe decreases. For example, a new smooth pipe has a roughness factor of C = 140, while a rough pipe is usually at C = 100. To determine an equivalent pipe, you must assume any of the above two properties. Therefore, for a system of pipes with different diameters, lengths, and roughness factors, you could assume a specific roughness factor (most commonly C = 100) and diameter (most commonly D = 8"). The most common formula for computing equivalent pipe is the Hazen-Williams formula:

Example 1:

Find the length and diameter for an equivalent pipe to replace 2000' of 12" pipe and 1000' of 16" pipe connected in series, each having C = 100.
Return to the Pipes page.