Friction loss is usually expressed in terms of which measurement?

Friction loss in firefighting is commonly expressed in pounds per square inch (psi) per 100 feet of hose. This standard measurement allows firefighters to accurately assess and calculate the pressure loss that occurs as water travels through hoses due to friction between the water and the inner walls of the hose. Knowing the friction loss per 100 feet provides a practical and easily manageable reference for crews when laying out hose lines and determining the total pressure needed at the pump to ensure sufficient flow at the nozzle.

By using this uniform measurement, firefighters can appropriately adjust their pumping efforts based on the length of hose deployed, making it a crucial concept for effective water supply management in firefighting operations. The other options express friction loss in different increments or units, which are either less common or more complicated for practical application in fire scenarios.