How is pump discharge pressure (PDP) calculated in relation to friction loss?

The calculation of pump discharge pressure (PDP) incorporates the net pump pressure (NP) and friction loss (FL) to ensure that the system maintains adequate pressure for efficient firefighting operations. When determining the PDP, you add the friction loss to the net pump pressure.

This is because the friction loss represents the pressure that is lost due to the resistance of water moving through hoses, fittings, and other components of the fire service water delivery system. To achieve the desired discharge pressure at the nozzle or related equipment, you must account for this loss by adding it to the net pressure provided by the pump.

Thus, when the pump is supplying water, the effective pressure available at the discharge point must compensate for any losses encountered, justifying the formula where pump discharge pressure is calculated as the sum of net pump pressure and friction loss.