Designing water systems and installations - Fluid mechanics approach

Designing a water supply network (including the supply of water for human consumption), and a wastewater evacuation and treatment system, requires close attention to the fundamental laws governing fluid mechanics. The expression of velocity and energy, and the equations determining the flow of liquids in cylindrical pipes, are all concepts necessary for pipe design calculations. Definitions and concepts such as peak and simultaneous weighting coefficients, base, probable, simultaneous and instantaneous flow rates are used to aid the theoretical approach. Based on requirements, specific calculation elements are also determined for pipes, whether for conveyance, supply, sewage or black water. Rainwater has other basic data, such as the average intensity of precipitation and the runoff coefficient, characterizing the retention capacity of a surface.

Flow conditions inside pipes are directly affected by flow rate, fluid velocity and pipe diameter, as well as by the resulting pressure drop. These aspects are covered in [TBA2516] .

Pipe sizing, which depends on the pipe material, its type (cast iron, steel, polished cement, concrete, plastic) and the quality of its inner wall, is covered in article [TBA2517] .