The Sewerage and Water Board of New Orleans (SWBNO) has been using acoustic leak detection technology as part of its water loss management and pipe integrity assessment program for nearly two decades. Early last year, it began incorporating more advanced acoustic-based leak detection and pipe condition assessment methods into its operations to more effectively identify structural problems in its transmission mains and water lines. The technology is helping the city save millions of gallons of water from being lost before it reaches customers.

After one of SWBNO’s flow meters was repaired and installed by Mississauga, Ontario, Canada-based Echologics on a 50-inch water transmission main in early October 2011, engineers from the company noticed unusual flow increases at odd times. Suspecting that a leak was the cause, the engineers acoustically surveyed smaller mains that branched off the transmission main.

To conduct the survey, engineers placed two sensors on valves and fire hydrants connected to selected sections of the water system. Then, a correlator listened for variations of acoustic signals in the pipe caused by flowing water from fire hydrants, physically tapping on appurtenances such as valves, or by attaching vibro-mechanical shakers to the system.

Changes in the acoustic signals pointed engineers to a large leak caused by a blown-off hydrant lead in a remote area located near a road embankment. Water was flowing out of the leak into a nearby drainage ditch. SWBNO crews immediately repaired the leak. Engineers later compared the transmission main’s historical flow data to the data collected after the leak was repaired and found that the leak had been responsible for losing at least 7.2 million gallons of water per day.

“Integrating acoustic-based leak detection and pipe condition assessment technology into our water loss management and water pipe integrity assessment program enabled us to detect and locate the leak. This leak would have likely remained unnoticed for at least six months due to its remote location, and might have continued to go unnoticed until secondary failure of the nearby roadway occurred,” says Steve Bass, utility services administrator for SWBNO. “Not only did the project help us to reduce millions of gallons of non-revenue water, it probably averted a dangerous and expensive catastrophic roadway failure.”