Friction loss is the...

• A. Varying flow rate due to elevation
• B. Resistance to flow
• C. Loss of pressure in terms of feet of hand per unit of pipe length
• D. Change in liquid density

Answer: (C)

Friction loss is the pressure drop caused by friction as liquid moves through a pipe, and it’s expressed as feet of head lost per unit length of pipe. This helps you quantify how much pressure is consumed by the pipe walls over a given distance (for example, feet of head per 100 feet of pipe). It’s the specific measure of resistance from internal pipe friction, not the static pressure change due to elevation. The other ideas don’t fit because elevation affects static head rather than friction, and a general statement of resistance doesn’t specify the per-length pressure- loss measurement. Change in liquid density isn’t what friction loss describes.