Friction Loss Calculations Explained:

Friction loss occurs when water passes through a fire hose. Distance, diameter, and the GPM / volume, all affect friction loss. As water passes through a fire hose, friction between the water and the inside surface of the hose cause turbulence. This turbulence reduces the energy produced by the pump (PSI). As a result, the PSI at the other end of the hose will be lower. The higher the gpm passing through a hose or pipe, the more turbulence and friction loss will result.