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This paper presents a methodology for the technical and economical design of agricultural horizontal drainage network. A drainage study uses data obtained from, among others, topographical, hydrological, hydro geological and soil studies as well as experimental laboratory research. The soil samples taken from the field are analyzed to establish the physical and chemical indexes of the soil, in order to determine the suitability and the endurance of mole drainage in the specified type of soil. The laboratory research is focused on establishing the hydraulic parameters of drainage materials (pipes and filtering materials), namely, the initial hydraulic conductivity (before silting), the resistance coefficient of water entering the drainage pipe, silting level, hydraulic conductivity after silting and the coefficient of hydraulic efficiency. Together with these data and a reference to Ernsts formula in which if must be determined, we can use Davids formula to calculate the hydraulic resistance coefficient of water (i or if ) entering in the drainage pipe and filtering material. Knowing this coefficient (i or if ), we can then determine the distance between the drainage pipelines through Ernsts formula by estimating the local hydraulic effects in the proximity of the pipelines in different situations. The important elements are the geometrical and functional parameters of drainage pipe and filtering materials, especially the hydraulic conductivity after silting. The methodology involved simulations of the real work of a drainage system under field conditions in the laboratory for a period of 1 to 2 months. From these experimental results, safe and reliable drainage solutions were then evaluated. For each type of soil tested, we studied at least three drainage solutions: without filtering material, or, with several different filtering materials. For each drainage solution studied, it was found that the cost of laying drainage pipelines for one kilometer could be used to compute the investment cost for the entire drainage network. Based on these findings, we could choose the most suitable economical and technical drainage solution, which would require the lowest investment outlay and the highest durability for the drainage network. This paper presents the results of the drainage studies for the representative types of soil from the North Western part of Romania (Timis, Arad, Bihor, Maramures and Satu Mare counties).