To determine friction loss, you need to know what?

• A. Temperature of water
• B. Pipe size
• C. Pipe size, flow, and c-factor
• D. Material hardness

Answer: (C)

Friction loss comes from the energy that water loses as it rubs against the inside of a pipe, and calculating that loss requires three things: the pipe’s size (diameter), the amount of water moving through (flow), and how rough the pipe’s interior is (the c-factor or roughness). The diameter controls the space water has to move; a larger diameter reduces friction. The flow determines how much interaction with the walls occurs—more flow means more friction. The roughness coefficient captures the effect of surface texture and age; a rougher surface creates more turbulence and energy loss. Temperature of the water and material hardness aren’t direct inputs in the standard friction-loss formulas, so they don’t determine the loss in the same way. That’s why the best answer includes pipe size, flow, and c-factor.