Which of the following factors does not materially affect the friction loss in a pipe?

Friction loss in a pipe is primarily influenced by the characteristics of the pipe and the fluid flowing through it. Factors such as the length of the pipe, the diameter of the pipe, and the velocity of the fluid are critical in calculating friction loss. Longer pipes create more surface area for resistance, leading to increased friction loss, while a larger diameter decreases it because the flow has more space, reducing velocity and turbulence.

Water temperature can also influence friction loss; warmer water may have lower viscosity, affecting how easily it flows, and consequently, impacting friction loss calculations.

However, the hardness of water does not materially affect friction loss in consistent, measurable terms. Hardness generally pertains to the concentration of minerals like calcium and magnesium. While it can impact scaling or maintenance issues over time, it does not directly influence the hydraulic factors that contribute to friction loss within the pipe itself. Thus, it is not considered a primary factor in calculating friction loss.