Locating leaks from water supply pipes using the passive acoustic method

Acoustic techniques for locating water leaks make use of the noise created by water leaking from a pipe; most require contact with the pipe network. This paper reports on the location of leaks in urban environments using acoustic loggers at the ground surface itself, remote from the pipe. An increase in the root-mean-squared (RMS) acoustic signal amplitude of ∼7.5 to ∼12.5 dB above background was detected above leaks from both plastic and metal pipes. The peak frequency of the acoustic signal was ∼750 Hz above a metal pipe, decreasing to ∼400 Hz at a distance of 1 m. Plastic pipes had a lower source leak frequency (below 700 Hz) and dropped to ∼350 Hz at 1 m. Background noise was predominantly below 150 Hz, which was suppressed using a high pass filter. The RMS signal amplitude directly above the leak decreased with increasing pipe depth, but was detectable for all pipe depths (0.4–1.0 m) covered in this work. An array of acoustic sensors at the surface can successfully detect and locate leaks without direct access to the pipe network, providing a robust and rapid leak location method.