Abstract: The location of a leak in a pond liner made of a sheet of electrically insulating material, such a polyvinyl chloride, supported by an electrically conductive medium, an example of which is a salar, is determined by immersing a power electrode in an electrically conductive fluid within the pond and a second or ground electrode in the supporting medium and creating therewith an electric potential between the pond fluid and supporting medium. A detector, having a pair of spaced probe electrodes which are electrically connected, is introduced to the fluid near the power electrode with the ends of the probe electrodes adjacent the liner. The detector is rotated until a maximum current reading is obtained by a galvanometer electrically connected to the detector probes. With the probes so aligned with respect to the power electrode, the probes are cause to traverse the liner and the location of a leak is noted by a sharp change in the galvanometer reading as one of the probes passes over the leak.