What is the flow from a 2-inch nozzle using the ideal nozzle pressure formula gpm = 29.7 x d^2 x NP? (d in inches)

• A. 1063 gpm
• B. 800 gpm
• C. 1200 gpm
• D. 1400 gpm

Answer: (A)

Flow through a nozzle scales with the square of the nozzle diameter and linearly with nozzle pressure. Plugging in a 2-inch diameter gives 29.7 × (2)^2 = 29.7 × 4 = 118.8. Then the discharge in gallons per minute is 118.8 × NP, where NP is the nozzle pressure in psi.

To reach about 1063 gpm, NP must be around 1063 ÷ 118.8 ≈ 8.9 psi. So with a nozzle pressure near 9 psi, the flow comes out around 1063 gpm. The key idea is that doubling the diameter increases flow by a factor of four (since d^2), and increasing nozzle pressure increases flow linearly. In real use, the ideal formula assumes an efficient, smooth bore with minimal losses.