Which combination should be used to achieve 1250 GPM on a deck gun requiring maximum GPM?

Which combination should be used to achieve 1250 GPM on a deck gun requiring maximum GPM?

• A. 2 inch tip at 110 psi
• B. 2 inch tip at 100 psi
• C. 1.75 inch tip at 110 psi
• D. 1.5 inch tip at 120 psi

Answer: (A)

Flow from a deck gun comes from two main factors: how big the nozzle opening is and how much pressure pushes water through it. The water flow increases with the size of the opening (the diameter) and with nozzle pressure, but the relationship isn’t linear. Roughly, increasing the diameter has a big impact because flow scales with the square of the diameter, while increasing pressure helps but to a lesser degree, following a square-root relationship. So, a 2-inch tip at 110 psi will deliver more GPM than a 2-inch tip at 100 psi, and both will exceed what you’d get from a smaller tip even if that smaller tip has higher pressure. The 1.75-inch tip at 110 psi loses flow mainly due to the smaller opening, and the 1.5-inch tip, even at 120 psi, cannot overcome the much smaller diameter. Therefore, the combination with the largest opening and a higher, but safe, nozzle pressure yields the maximum GPM.

Flow from a deck gun comes from two main factors: how big the nozzle opening is and how much pressure pushes water through it. The water flow increases with the size of the opening (the diameter) and with nozzle pressure, but the relationship isn’t linear. Roughly, increasing the diameter has a big impact because flow scales with the square of the diameter, while increasing pressure helps but to a lesser degree, following a square-root relationship.

So, a 2-inch tip at 110 psi will deliver more GPM than a 2-inch tip at 100 psi, and both will exceed what you’d get from a smaller tip even if that smaller tip has higher pressure. The 1.75-inch tip at 110 psi loses flow mainly due to the smaller opening, and the 1.5-inch tip, even at 120 psi, cannot overcome the much smaller diameter. Therefore, the combination with the largest opening and a higher, but safe, nozzle pressure yields the maximum GPM.