What is the recommended method for determining the exact friction loss of any appliance?

• A. Check NFPA 1091
• B. Run tests with each appliance used by the department
• C. Review manufacturer's specifications
• D. Check NFPA 1901

Answer: (B)

Friction loss through an appliance isn’t a fixed number you can look up; it changes with how the equipment is configured and how much water you’re moving. To know the exact friction loss for the department’s setup, you measure it directly on the appliances you actually use. That means running tests with each appliance under your usual operating conditions—the same nozzle, the same hose length and diameter, the same fittings, and the target flow—and recording the pressure drop across the appliance. In practice you compare the pump discharge pressure to the nozzle pressure (or measure pressures before and after the appliance) at the desired flow, and the difference is the friction loss of that appliance in your system. Manufacturer specifications can give general figures, but they may not reflect your specific hose, fittings, or installation. Standards related to apparatus define requirements and qualifications, not the exact method for measuring friction loss. So testing with the department’s own appliances provides the precise, repeatable friction loss for your setup.