Composite liners comprising a geomembrane with a circular hole, a geosynthetic clay liner and a compacted clay liner were studied in tests conducted at three scales to measure the flow rates at the interface between the geomembrane and the GCL and in the composite liners. The tests conducted aimed at studying the influence of the prehydration of the GCLs, the influence of the confining stress, and the influence of the hydraulic head on flow rates through composite liners due to defects in the geomembrane. Another goal of these tests was to check the feasibility of an extrapolation of results obtained from small-scale tests to field conditions. Results indicate that the prehydration affected flow rate in a different way according to the confining stress applied and the GCL used. They also indicate that the flow rate decreases with the increase in confining stress and that this effect is higher for prehydrated GCLs than for non-prehydrated GCLs. Results show as well that the flow rate increases when the hydraulic head increases. Finally, small-scale tests overestimate the flow as compared to intermediate and large-scale tests and thus flow obtained in small-scale tests represent an upper bound of flow that would be obtained in field conditions.