Geotextiles are widely used for drainage in earth and construction works. In the EN ISO standards the drainage function is defined as ”The collecting and transporting of precipitation, ground water and/or other fluids in the plane of the geotextile”. In other words, it is the ability of the geotextile to drain fluids on its own, meaning that it is not part of a drainage system, but is the drainage system itself. The drainage function is often confused with the filtration function. When a geotextile is part of a drainage system, where it is used to separate a soil and a coarse-grained drainage layer, the function is filtration.Usually, the installation strains are limited and use does not apply significant mechanical strains to a drainage geotextile. Consequently, high mechanical strength is not required, whereas hydraulic properties are decisive for the overall performance of the entire construction, with the water flow capacity in the plane of the geotextile being the most important.