PUB adopts smart tools to detect and preempt pipe leaks New technologies help to minimise water loss from underground water pipes

PUB ADOPTS SMART TOOLS TO DETECT AND PREEMPT PIPE LEAKS

New technologies help to minimise water loss from underground water pipes.

Precious water can be lost through leaks and cracks in aged pipes over time and it is extremely difficult to locate such ‘hidden’ leaks until water reaches the ground surface or shoots up due to the pressure in pipes. By turning to smart tools and new technologies such as leak monitoring sensors, inline pipe inspection tools and smartphone sensors, PUB, Singapore’s National Water Agency, seeks to enhance its leak detection capabilities to reduce water loss. A network of 5,700 km of water pipelines conveys clean potable water to 1.6 million customers, island-wide. PUB has, in place, a comprehensive pipe maintenance and renewal programme, to ensure the water pipes and fittings are always in good working condition. Through regular inspection and replacement of old and leak-prone pipes, PUB now records 5 leaks per 100 km of pipes per year, which is about the lowest incidence of leaks in the world. In 2014, PUB recorded 10 leaks per 100 km of pipes. As most pipes are underground, small leaks often go unnoticed and eventually develop into bigger leaks. With the use of acoustic sensors and innovative technologies, PUB has been able to locate and repair developing leaks before a pipe burst occurs. This will reduce water service disruption to customers, as a badly leaking pipe would need to be shut-off for repairs.

Smart tools for more accurate and effective leak detection

Leak monitoring sensors were first trialled in 2017, with 120 sensors installed along approximately 70 km of large water mains, for early detection of developing leaks. These sensors work by monitoring and analysing noise characteristics in pipes, to determine the presence of leaks. The data is collated in a centralised server, and advanced analytics are used to interpret readings and alert PUB automatically when a leak is identified. The sensors can accurately identify a leak along the pipe and determine its location within 3 m of the leak. The trial was successful, with the sensors detecting 13 leaks over a three-year period. In one incident, in 2018, the sensors alerted PUB to a potential leak on a 700 mm diameter water pipe alongside a major expressway. Upon excavation, a 13 mm hole was discovered at the bottom of the pipe, within 0.5 m of the location reported by the sensors. The hole was created due to corrosion. This early detection allowed PUB to promptly repair the pipe and prevent further water loss. Following on from the trial, PUB plans to progressively scale up the number of sensors in the network and deploy 1,200 sensors for leak monitoring, islandwide, by 2021.

Leak monitoring sensor

PUB is also exploring the use of inline pipe inspection tools for leak detection in large water mains. The tool is inserted directly into the pipe, which allows for more targeted and precise inspection of the pipe wall, to detect any cracks or anomalies. Propelled by the flow of water in the pipe, these tools can easily survey long stretches of a pipe in a single deployment. One such tool is a ballshaped sensor that can determine the leak location to an accuracy of 2 m, by picking up acoustic or noise signature related to the leaks. PUB will be deploying these sensors to survey 500 km of pipes over the next five years. For smaller water pipes, the PUB leak detection teams were recently equipped with smartphone sensors, a portable and easy-to-use survey tool that has proven to be effective in locating leaks. The sensor, connected to a smartphone, is placed on pipe fittings such as hydrants and valves to pick up sounds from the pipe. The smartphone automatically digitalises and analyses the acoustic signal in real-time via a dedicated mobile application to check for leaks. Two sensors can be deployed on separate pipe fittings at once, to correlate their readings and determine the leak location within 2 m along the pipe.

Inline pipe inspection tool Listening stick

Noise logger and correlator

Smartphone sensor

Mr Ridzuan Ismail, PUB’s Director of Water Supply (Network) said, “PUB is always on the lookout for new technologies for early leak detection, so that we can minimise water loss in the network and increase the resilience of service that we provide to our customers. With intelligent leak monitoring and detection technology, we are taking a more preventive and predictive approach and moving away from a resource-intensive operation that requires very specialised skills. This will bring us closer to our goal of transforming our operations through digitalisation, to become a smart utility of the future”.

Evolution of leak detection methods over the years

In the early days of leak detection, operators and engineers listened for noise generated by water escaping, under pressure, from buried pipes. In the 1970s, mechanical tools such as listening sticks were used to locate pipe leaks. They had limited accuracy as they relied on the hearing and experience of the engineer. There could also be interference from ambient noises in the environment, such as from passing vehicles. Nonetheless, listening sticks are highly portable and particularly useful to confirm the precise location of the leak on site, prior to ground excavation to reach the pipe.

Correlation graph showing leak detected in water pipe

In the early 2000s, PUB started deploying noise loggers and correlators for more dynamic leak detection. Deployed during the night, the noise loggers would be used to inspect large areas of the pipe network and localise the leak to within a 100 m stretch of pipe. Thereafter, the correlators were used to determine the actual leak location on the pipe. Listening sticks, as well as noise loggers and correlators, are still in use today to complement the suite of tools for effective leak monitoring and detection.

Public feedback

Public feedback is also an important channel that PUB taps on for leak detection. PUB’s call centre operates 24 hours a day.

All images by PUB, Singapore's National Water Agency