Abstract: A water leak detection system for generating a control signal indicative of a water leak detection. The system is connectable to a power line carrying an AC power signal. The system includes a master unit connectable to the power line for generating the control signal indicative of a water leak detection. One or more slave units are connectable to the power line for communicating with the master unit. One or more sensors are connected to the slave unit for detecting a water leak. A communication system transmits and receives data signals between the master unit and each slave unit in the AC power signal. The communication system includes an encoder for encoding outbound data into the AC power signal using frequency shift keying (FSK) signals and a decoder for decoding inbound frequency shift keying (FSK) signals from the AC power signal.