Fire Officer's Handbook of Tactics Practice Test 2025 – Comprehensive All-in-One Guide to Master the Exam!

When the diameter of the hose is decreased, friction loss (FL) increases due to the principles of fluid dynamics. The relationship between hose diameter and friction loss can be explained through the Darcy-Weisbach equation and other hydraulic calculations, which indicate that as the diameter of the hose decreases, the velocity of the fluid must increase to maintain the same flow rate.

As the velocity increases, the friction loss increases exponentially, as it depends on the square of the velocity. This heightened turbulence and increased interactions between the fluid and the inner walls of the hose contribute to greater energy loss in the form of friction loss. Therefore, in firefighting operations, using narrower hoses can lead to significant increases in friction loss, which makes it more challenging to deliver the desired flow rates effectively.