The flexible lay flat hose will swell in diameter when pressureized, causing a lower pressure drop than compared to a rigid hose. The data is based on internal hose diameter, and the actual pressure drop is therefore some lower. Variables such as fittings and bends increase the frictional losses and an estimate of their effect may be determined by adding an “equivalent length” to the hose length. Values of the equivalent length (Le) may be determined using the internal diameter (D) of the hose in the following relationship:
