You are supplying Truck 7 through dual 3" lines to their rear inlets, and the truck needs 165 psi at the inlet. If your hydrant pressure is 45, what is the friction loss calculation?

To determine the correct friction loss calculation, it's important to understand the relationship between the required inlet pressure, the hydrant pressure, and the friction loss in the hoses.

The truck needs 165 psi at its rear inlets. This is the pressure required for proper operation. The hydrant pressure available is 45 psi. To find the friction loss in the hoses, you can use the following formula:

Friction Loss = Required Inlet Pressure - Hydrant Pressure.

Substituting the values gives us:

Friction Loss = 165 psi - 45 psi = 120 psi.

However, the options presented do not include 120 psi. To reconcile this, typically in firefighting, additional pressures can be accounted for in water supply calculations, such as elevation changes and hose diameter. If you utilize the standard friction loss per 100 feet for 3-inch hose, which is often around 5 psi per 100 feet for a flowing condition, you would need to consider how the total length of hose in use contributes to the total friction loss, potentially when estimating the length of dual lines.

While 120 psi would be a straightforward calculation, the presence of 170 psi in the answer choices suggests that there may be a scenario where