During the last decades, the importance of sustainable development in society has increased considerably. Sustainable Urban Drainage Systems (SUDS) are a group of techniques that aim to improve the management of rain and run-off water while reducing their pollution. Many of these systems incorporate geotextiles in their structures, which act as a layer separation and water filter. Some authors defend the idea that by simply being installed, geotextiles partially or totally lose their separation and filtering capacities. This study proposes a testing methodology that can reproduce this effect and obtain a reduction factor for the water permeability of the material after its installation, which is defined here as the 'new condition factor'. The procedure simulated the real installation conditions in the laboratory by causing the specimen to undergo both mechanical and hydraulic damage and subsequently measuring the loss of water permeability that it provoked on the geotextile. Two different nonwoven geotextiles were tested in order to validate the procedure and to obtain initial results that could confirm the need for the new condition factor in the design of pervious pavements with geotextiles. Analysis of variance (ANOVA) was used to determine the statistical significance of the test variables.