What does the C factor relate to in pipe hydraulics?

• A. pipe material
• B. flow velocity
• C. interior roughness and friction losses
• D. service temperature

Answer: (C)

The C factor in pipe hydraulics is tied to how rough the inside of the pipe is and how that roughness causes friction losses as water flows. In many design formulas, this coefficient acts as a roughness term: smoother interiors yield a higher C value and less friction, so for a given driving head or slope you get more flow, while rougher, older, or fouled interiors lower the C value and increase friction losses, reducing flow. It’s not about the pipe’s material in isolation, the velocity of the flow, or the service temperature; it specifically consolidates how interior roughness and resulting friction losses affect the relationship between flow and head loss.