In the friction loss formula FL = C × Q² × L, what does C stand for?

• A. Friction loss coefficient for the hose diameter
• B. Flow rate in GPM
• C. Length factor
• D. Constant of proportionality unrelated to hose size

Answer: (A)

In this formula, the friction loss per unit length is determined by three pieces: how much water is moving (Q), how long the hose runs (L), and a coefficient that captures the hose’s characteristics. The coefficient C is the friction loss coefficient for the hose diameter. It represents how the hose’s size, inner surface, and roughness affect energy loss due to friction at a given flow. Because different hose diameters have different internal finishes and surface interactions with the water, C varies with diameter and is essentially a diameter-specific factor you look up or determine for that hose.

That’s why the other ideas don’t fit: Q is the flow rate and appears as Q squared, and L is the actual hose length; C is not that flow or length, and it isn’t a universal constant—its value depends on the hose diameter (and its roughness). So the correct interpretation is that C stands for the friction loss coefficient for the hose diameter.