One of the most important issues to consider in the choice of water pipelines is the “values of the internal pipe roughness coefficient”, experimentally verified, with which the main pressure drops on the pipeline are calculated.

Some factors, as the smoothness of the surface, the number of special components and hydraulic equipments along the pipline and the friction of the water itself (depending on its viscosity), determines an uncertainty decides that the coefficient is measured in range and not in absolute values.