As the C-factor of a pipe increases, what happens to the smoothness of the pipe?

The C-factor, or Hazen-Williams coefficient, quantifies the roughness and subsequent friction loss of a pipe in water distribution systems. As the C-factor increases, it indicates a smoother pipe surface. A higher C-factor corresponds to less resistance to flow, meaning that water can move more freely through the pipe due to reduced friction.

This relationship holds because smoother surfaces allow for greater flow efficiency. Hence, if a pipe has a higher C-factor, it demonstrates better hydraulic performance and lower energy losses due to friction. Understanding this concept is crucial for water distribution design, as selecting pipes with appropriate C-factors can significantly impact system efficiency and operational costs.

In contrast, if the C-factor were to decrease, it would suggest a rougher surface, leading to increased friction loss, and potential issues with flow rates and energy consumption, which is not the case here. Therefore, the correct answer directly aligns the increase in C-factor with increased pipe smoothness.