What is the elevation pressure when the nozzle is on the 11th floor?

To determine the correct elevation pressure when the nozzle is on the 11th floor, one needs to understand how elevation affects pressure in firefighting scenarios. The basic principle involved is that water pressure decreases as you go higher in elevation due to the weight of the water column above the nozzle.

Typically, a good rule of thumb used in the fire service is that for every foot of elevation gain, approximately 0.434 psi is lost. Therefore, when calculating the pressure loss due to elevation, one must first determine the height in feet for the 11th floor. Assuming that each floor is roughly around 10 feet tall, the height of the 11th floor would be approximately 110 feet.

When you multiply the height by the pressure loss factor, you get:

110 feet * 0.434 psi/foot = approximately 47.74 psi.

In practical applications, this value would be rounded to a standard operational pressure. Hence choosing about 50 psi accounts for the pressure that would still be effective for fire suppression when using a nozzle on the 11th floor. Correctly identifying the elevation pressure is crucial for ensuring adequate water flow and effective firefighting operations, making 50 psi an appropriate choice in this scenario.