Locating leaks from water supply pipes using the passive acoustic method A. Lockwood, T. Murray, G. Stuart and L. Scudder ABSTRACT A. Lockwood Westlakes Scientific Consulting Ltd, The Princess Royal Building, Westlakes Science and Technology Park, Moor Row, Cumbria CA24 3LN, UK, and Faculty of Earth and Environment, University of Leeds, Leeds LS2 9JT,UK T. Murray (corresponding author) Department of Geography, University of Wales Swansea, Singleton Park Swansea SA2 8PP,UK G. Stuart Faculty of Earth and Environment, University of Leeds, Leeds LS2 9JT,UK L. Scudder Thames Water PLC, Spencer House, Manor Farm Road, Reading, RG2 0JN,UK 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. Key words | shallow acoustic, urban environment, water leak location, water supply INTRODUCTION The provision of drinkable water is regarded as a basic right in the developed world and considerable time and money is expended in supplying and maintaining this food grade product (Pickerill & Malthus 1998). The reduction of leakage from the potable water network is an important element in the strategy to achieve sustainable use of this essential resource (Pilcher 2003). Water leakage levels are often given as a percentage of distribution input, and values of 30% are not unheard of (e.g. Jowitt 1995; Torsun 1998). The key to a successful leakage management programme is the rapid location and subsequent repair of leaks from the network (Farley & Trow 2003). Rapid leak location and repair both reduces the water lost (i.e. wastage) from the network and the damage caused by the water from the leak (Pilcher 2003). Accurate and precise location of water leaks is the most important aspect of the leak to water companies; this is followed by the size of the leak and finally the depth to the pipe itself. This paper reports on the use of an array of surface acoustic recorders to detect leaks from water pipes and investigates the variables involved by analysing a number of case studies. This technique removes the dependency of the acoustic method on the need for access to the pipe. It has particular advantages when applied to leaks from plastic pipes, where fittings may not be closely enough spaced for standard leak location techniques to be successful, as the acoustic attenuation in plastic pipes is greater than that suffered in metal pipes (Hunaidi et al. 1999; Farley & Trow 2003). Acoustic methods of leak detection make use of the sound waves created when pressurised water is forced out through holes and cracks in the water pipe network (Liston & Liston 1992). These bi-directional vibrations propagate through the water and along the pipe wall (Grunwell & Ratcliffe 1981; Muggleton et al. 2002; Covas et al. 2004), and radially out into the subsurface (Pickerill & Malthus 1998). 519 Q IWA Publishing 2005 Journal of Water Supply: Research and Technology—AQUA | 54.8 | 2005 Downloaded from http://iwaponline.com/aqua/article-pdf/54/8/519/402713/519.pdf by guest on 20 November 2023