In this study, a novel algorithm to locate regions in a distribution feeder, where power is being illegally tapped, is proposed. The basic requirements of the algorithm are voltage measuring devices located at distribution feeder nodes or transformers that can communicate data to the distribution substation. Initially, how voltage magnitude difference between successive nodes in a feeder can help identify possible locations of illegal tapping is shown. The technique is further refined by a normalised voltage double difference method, to pin-point the exact location of power theft. The algorithm does not require network parameters. Simulations are performed on the IEEE 34 node test feeder, to demonstrate the efficacy of this method.