How much pressure is needed for 800 feet of 5" LDH?

To determine the amount of pressure needed for 800 feet of 5-inch Large Diameter Hose (LDH), it's essential to understand the general rule of thumb related to the friction loss in hoses. For LDH, the friction loss typically is about 1 psi per 100 feet of hose when flowing water.

In this scenario, with 800 feet of 5-inch LDH, you would calculate the friction loss as follows:

1. For every 100 feet, you would expect approximately 1 psi of pressure loss due to friction.

2. Therefore, for 800 feet, the friction loss would be 8 psi (since 800 divided by 100 equals 8).

In addition, the required pressure also depends on the desired discharge pressure at the nozzle, which may be influenced by factors such as the type of operation or condition of the fire scene. Assuming a common discharge pressure at the nozzle of 30 psi is required for effective firefighting operations, you would combine this with the friction loss:

30 psi (discharge pressure) + 8 psi (friction loss) results in a total of 38 psi.

It is conventional rounding in firefighting operations that may lead to specifying 40 psi to ensure a sufficient safety margin