AbstractIn this study, a gradient ratio test which is one of the methods used in the laboratory to evaluate the clogging potential of soil‐synthetic envelope systems was applied. For this purpose, two physical models of permeameters (designed by ASTM D‐5101) were used to carry out a series of permeability tests by applying water with different salinities and five different PLMs (pre‐wrapped loose material). To simulate real conditions, soil and water were collected from the Khorramshahr drainage project area located in Khuzestan province (south of Iran) which has been significantly encountering the common trouble of water and soil salinity. Therefore, saline drainage water (EC =22.2 dS m−1, SAR =26.27 (meq l−1)0.5) in comparison with low salinity water (EC =0.78 dS m−1, SAR =1.23 (meq l−1)0.5)) were considered in this research. Permeability tests were carried out at five different hydraulic gradients (1, 2.5, 5, 7.5, and 10) according to the standard method. Variations of system permeability and gradient ratios were investigated statistically as factorial experiments in the form of a randomized complete design. Based on the permeability test results, hydraulic conductivity and gradient ratio of all PLMs were susceptible to the salinity of the water utilized in permeability tests. Based on the results of all gradient ratios, the probability of clogging by applying saline water was higher. Copyright © 2014 John Wiley & Sons, Ltd.