The French regulation on waste landfilling is under review. The use of drainage geocomposites will be allowed to replace part of the granular drainage layer at the bottom of landfills provided equivalence is demonstrated. In this instance the knowledge of the behaviour of drainage geocomposites on the long term has to be improved. Water flow capacity in the plane tests were performed with 4 drainage geocomposites selected for their various types of drainage cores, during 7 days, with two types of contact area, either by applying the load through a rigid plate on the geocomposite or through a foam layer in the testing equipment of EN ISO 12958. These tests were performed under a 200 kPa load. Results obtained will be given. They allow to evidence the influence of the type of the contact area on the hydraulic performance of the products. Thanks to this work, the intrusion phenomenon of the filter inside the geospacer could also be identified and quantified to be introduced in the long term design of in-plane flow capacity of drainage geocomposites with other parameters like the compressive creep behavior of the drainage core. These test results were used to update (1) a guide on drainage and filtration recently published by the French chapter of the International Geosynthetics Society, and (2) the French standard NF G38-061 dedicated to the design of geosynthetic drainage systems.