Geosynthetics are polymeric materials that are incorporated in soil to improve the physical soil conditions and to provide better soil drainage capability. Geosynthetics are divided into five categories of geotextiles, geogrids, geonets, geomembranes and geocomposits. Geotextiles are the most important subdivision of geosynthetics. Geotextiles are porous and permeable fibrous which usually are made of polymeric fibers. Geotextiles among many other uses can be used as envelope or filter for drainpipes. The geotextiles, because of its porosity improve hydraulic performance of drainpipes and protect them from sediment. The geotextiles are capable of preventing migration of soil particles into the drain which causes clogging. In this study, the effects of geotextiles structural parameters on water permeability, clogging and clogging changes for the needled nonwoven geotextile samples were investigated. Needled geotextile samples with various mass per unit area, thickness and porosity were produced and tested using commercially available melt-spun staple polypropylene fibers. These geotextiles samples were named G1, G2 and G3. Experiments were conducted using two soil samples with different grain size distributions named S1 and S2. Based on ASTM D4833 standard, the resistance of the geotextile samples was determined. Then, the permeability of geotextile samples and soils were measured according to ASTM D5493 standard. Drainage envelopes are exposed to clogging and therefore their resistance needs to be determined. Therefore, a testing device which was able to evaluate the clogging potential and permeability of the samples was designed and constructed according to ASTM D5101 standard. Using the device, the permeability of geotextile samples for both soils were measured. The permeability were measured with time. The gradient ratio which is defined as the hydraulic gradient of soil-geotextile assembly to soil hydraulic gradient was used to determine the clogging potential of geotextiles. Using currently available equations, gradient ratio at each standard hydraulic gradient was calculated and the changes in gradient ratio were determined for each geotextile samples. Results showed that G2 geotextile which has the highest mass per unit area and thickness in comparison to other samples has the highest resistance and the lowest permeability. The increase in hydraulic gradient caused reduction in infiltration for the samples. Results showed reduction of the geotextile permeability due to increase in the mass per unit area. Utilization time tended to reduce permeability of the geotextile-soil assembly. The increase in utilization time leads to increase gradient ratio. The G1 and G2 geotextiles which had gradient ratios greater than unity easily clogged. The G2 geotextile as compared to the G1 geotextile clogged faster. The G3 Geotextile which requires fewer punch density, due to gradient ratio smaller than unity, is more suitable for drainage of sample soils. Keywords: Geotextile, Drainpipe, Clogging, Permeability, Gradient Ratio