For calculating friction loss in a pipe, which factor is not required?

• A. Temperature
• B. Pipe size
• C. Flow
• D. C-factor

Answer: (A)

When you calculate friction loss in a pipe, the variables that drive the loss are how much water is moving (flow), the size of the pipe (diameter), the length the water travels, and the roughness of the pipe’s interior (captured by the C-factor or friction factor). Temperature isn’t part of those standard inputs. The Hazen-Williams equation uses the C-factor to reflect material roughness and age, and the Darcy-Weisbach approach uses a friction factor that depends on roughness and Reynolds number, which is based on viscosity–density assumptions for water. In typical practice, water temperature isn’t needed because those properties are treated as constants or are embedded in the chosen C-factor or friction factor. So temperature isn’t required for the friction-loss calculation.