Explain the relationship between nozzle pressure and GPM.

• A. Nozzle pressure is independent of GPM.
• B. Higher GPM generally requires higher nozzle pressure, but nozzle design determines the precise pressure required.
• C. Higher GPM always reduces nozzle pressure.
• D. Nozzle pressure equals atmospheric pressure.

Answer: (B)

GPM and nozzle pressure are linked by the resistance the water faces as it flows through the hose and the nozzle itself. When you want more water to come out (higher GPM), you generally have to push harder, so the pressure at the nozzle increases. The nozzle’s design—its orifice size and internal shaping—determines exactly what pressure is needed to achieve a given flow and pattern. A nozzle with a larger orifice can deliver more GPM at the same pressure, or deliver the same GPM at a lower pressure; conversely, a smaller orifice requires higher pressure to reach the same flow. In practice, you account for friction losses along the hose and fittings and any elevation changes, and you set the discharge pressure to reach the target GPM with that specific nozzle. So higher GPM usually means higher nozzle pressure, but the precise value is defined by the nozzle’s design.