What is the approximate gpm of water delivered from a 1-1/4-inch nozzle at 50 psi?

To determine the approximate gallons per minute (gpm) of water delivered from a 1-1/4-inch nozzle at 50 psi, we can use the formula that relates the nozzle size, pressure, and flow rate. For a smooth bore nozzle, there is a common rule of thumb that states that for each inch of diameter of the nozzle, the flow rate increases by approximately 100 gpm for every 10 psi of pressure.

In this case, a 1-1/4-inch nozzle has a diameter of 1.25 inches. Therefore, we can use the flow rate formula which typically estimates that a 1-inch nozzle delivers about 100 gpm at 50 psi, and you can expect an additional increment of 25% more for the 1-1/4 inch size, leading to about 320 gpm. Utilizing water flow equations, you may find that at 50 psi, the specific flow rate for a 1-1/4-inch nozzle is approximately 328 gpm.

This relationship explains why 328 gpm is the correct answer, as it reflects a practical and calculated estimation based on both the nozzle size and the pressure at which water is delivered. This calculation is crucial for firefighters