Does anyone know of a transmitter (Sound, Flow, Vibration, etc. etc.) to detect if a water main has failed? I have used excessive flow meters/detectors/sensors to perform this on natural gas piping systems but never on water main feeds that are buried.

I can meter the main feed to the complex of 18 buildings and meter the individual buildings and do a delta on total summation comparison (Very Expensive). Not sure of any other concepts?