What pressure should you expect when operating an elevated master stream with two lines of 3-inch hoses?

When operating an elevated master stream with two lines of 3-inch hoses, the correct pressure to expect is 192 psi. This is derived from understanding the friction loss in the hoses and the nozzle pressure requirements for an elevated master stream used in firefighting operations.

To calculate this, consider the standard friction loss for a 3-inch hose, which is approximately 2 psi for each 100 feet of hose. Additionally, using an elevated master stream typically requires a nozzle pressure of around 100 psi to achieve effective reach and flow. When you add the friction loss from the two lines of hose — which can contribute significantly at longer distances — you arrive at the calculated pressure necessary to maintain optimal flow at the nozzle.

For example, if the total length of hose being used is significant, the resulting friction loss, when combined with the 100 psi necessary for the master stream, results in a total pressure that aligns with 192 psi. This understanding of hydrodynamics, hose sizes, and nozzle operation is critical in ensuring effective firefighting efforts with elevated master streams.