What is the minimum pressure required at the nozzle inlet for a combination fog and straight stream nozzle using 1 1/2 in., 1 3/4 in., or 2 in. hose in lengths of 150 ft?

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

Answer: (C)

The main idea is that the pressure at the nozzle inlet must be enough to both meet the nozzle’s required operating pressure and overcome the friction losses in the supply hose over the distance to the nozzle. For a combination fog and straight-stream nozzle fed from 150 ft of standpipe hose in sizes around 1 1/2 to 2 inches, the hose friction losses add a significant amount to what the nozzle itself needs. When you add those friction losses to the nozzle’s required operating pressure for this type of nozzle, the resulting nozzle inlet pressure comes out in the mid-90s psi. That’s why 94 psi is the best choice among the options: it reflects the sum of the nozzle’s needs and the hose friction losses over 150 ft for these hose sizes. The other numbers either don’t provide enough pressure to overcome hose losses and operate the nozzle properly, or are higher than what’s required given typical friction losses for this setup.