A leak detection system having power and communication lines includes a leak sensing cable having sensor lines for sensing a leak, detection controllers connected to the sensor lines to detect a leak position signal, and a master controller receiving the detected leak position signal from the detection controllers, wherein the leak sensing cable includes power and communication lines that are wired to supply power to the detection controllers via the master controller and to transmit the leak position signal to the master controller from the detection controllers. According to this invention, the leak detection system has power and communication lines that are able to transmit the leak position signal between the detection controllers and the master controller while supplying power to the detection controllers and the master controller.