It describes the types of flow regimes, existing equations are demonstrated to calculate heado losses in laminar and turbulent regime and presents the boundary layer theory. The characteristics of the pipes most commonly used in agricultural facilities and their fittings and accessories are described. The main issues to consider in their installation: ditches and mechanical stresses. The process for calculating pressure loss in pipes is definded. The formulas and methods used to calculate continuous an singular head losses are presented. It describes the influence of altimetric profile of a pipeline in operation and calculation. Lines are calculated under different operating conditions as well as pipes in series and in parallel.