For a 150 ft run using 1 1/2 in, 1 3/4 in, or 2 in. hose with a combination fog and straight stream nozzle, what nozzle inlet pressure is required?

• A. 70 psi
• B. 110 psi
• C. 94 psi
• D. 130 psi

Answer: (C)

The key idea is that nozzle inlet pressure equals what the nozzle needs to operate properly plus the friction loss encountered along the hose run. For a combination fog and straight-stream nozzle, you typically need about 50 psi at the nozzle to achieve the required discharge pattern. Over a 150 ft hose run, the friction loss along the hose (which depends on diameter and flow) reduces the pressure you actually have at the nozzle inlet by roughly 44 psi for these hose sizes at the intended flow. Add those together and you get about 94 psi at the nozzle inlet. That makes 94 psi the best choice. The other pressures would either under- or over-feature the discharge for this setup.