System offers reliable method of water-pipe leak testing

Figures from Ofwat, the water services regulation authority for England and Wales, suggest that between 20 and 40 per cent of our total water supply can be lost through damaged pipes.

The system invented at Sheffield is said to test pipes by transmitting a pressure wave along them that sends back a signal if it passes any unexpected features, such as a leak or a crack in the pipe’s surface.

According to a statement, the pressure wave is generated by a valve fitted to an ordinary water hydrant, which is opened and closed rapidly. The wave sends back a reflection, or a signal, if it encounters any anomalous features in the pipe. The strength of that signal can then be analysed to determine the location and the size of the leak.

Originally developed by a team led by Prof Stephen Beck in the university’s Department of Mechanical Engineering, the invention was developed into a prototype device in partnership with colleagues in the Department of Civil and Structural Engineering, and Yorkshire Water.

The device has now been trialled at Yorkshire Water’s field operators training site in Bradford and results show that it offers a reliable and accurate method of leak testing.

Leaks in cast-iron pipes were located accurately to within 1m, while leaks in plastic pipes were located even more precisely, to within 20cm.

The results of the trial are published today, 6 August, in a paper entitled: ‘On site leak location in a pipe network by cepstrum analysis of pressure transients’, in the Journal — American Water Works Association.

Existing leak-detection techniques rely on acoustic sensing with microphones commonly used to identify noise generated by pressurised water escaping from the pipe. This method, however, is time consuming and prone to errors. The use of plastic pipes, for example, means that the sound can fall away quickly, making detection very difficult.

In contrast, the device invented by the Sheffield team uses a series of calculations based on the size of the pipe, the speed of the pressure wave, and the distance it has to travel. The device can be calibrated to get the most accurate results and all the data is analysed on site, delivering immediate results that can be prioritised for action.

Dr James Shucksmith, in the Department of Civil and Structural Engineering at the University of Sheffield, who led the trial, said: ‘We hope now to find an industrial partner to develop the device to the point where it can be manufactured commercially.’