Acoustic and ultrasonic techniques for defect detection and condition monitoring in water and sewerage pipes: a review

Condition monitoring for water and sewerage pipes is essential for the safety of the environment, energy conservation and human health. This paper focuses on the application of acoustic and ultrasonic techniques for the detection and assessment of leaks, blockages and defect in buried pipes. The review includes acoustic methods (below 20 kHz) based on vibration sensing using accelerometers, hydrophones and fibre optic sensors, and ultrasonic methods (above 20 kHz) based on the propagation of bulk and guided waves. Related data-driven, machine-learning techniques are also discussed. Typical arrangements of sensors are shown, explained and analysed in terms of their applicability to buried pipe networks. Commercial systems and state of the art research for the inspection of pipes made of a range of materials such as cast iron, high-density polyethylene and concrete are critically assessed. This review also explores the future application of autonomous robotics to deploy these sensors in water distribution and sewerage pipes.