Water Treatment and Distribution SystemThe measure of the roughness of a pipe’s interior surface that retards flow due to friction. The higher the C value, the smoother the surface which results in less friction. By jay@americanwatercollege.org | January 15, 2017 | Certification Exams . Distribution . Water Treatment | Tags: C Value (C Factor), Certification Exam Prep, Distribution Piping, Distribution System, Water Treatment