The C-factor of a water pipe measures which property?

The C-factor, or coefficient, of a water pipe is primarily used to measure the interior roughness of the pipe. This value is crucial because it directly influences the hydraulic characteristics of the pipe, specifically how easily water can flow through it. A lower C-factor indicates a smoother interior surface, resulting in less friction and higher flow efficiency, while a higher C-factor suggests a rougher surface, which can impede flow and increase the resistance water encounters as it moves through the pipe.

Understanding the C-factor is essential for engineers and water distribution professionals as it helps in calculating flow rates and pressure losses in water distribution systems. The other choices, such as the diameter and length of the pipe, are important factors in water flow dynamics but do not pertain to the C-factor, which is specifically focused on the surface condition within the pipe.