Leak detection: back to the future with fibre optics?

Fibre optics have the potential to be a leak detection game-changer, despite a number of false dawns. We look at two projects that aim to prove the technology is viable, reliable, and cost-effective.

The leak detection challenge

Leak detection is one of the major challenges faced by the water industry. For many years, the use of fibre optic cables has been considered to have the potential to vastly increase the volume of leaks detected, as well as increasing the speed of detection. 

While the technology has been successfully tested, uptake has been poor thanks to the disruption involved in laying new cables and in circumnavigating valves.

In 2021, the Yorkshire Water-led TAWCO project highlighted both the possibilities and the challenges. A spokesperson for the company told Aquatech Online: “The project highlighted the transformative potential of fibre optics in leak detection, offering real-time monitoring and highly accurate leak detection information across extensive water networks.”

The project struggled to gain Regulation 31 approval, i.e. proving that the of the cables did not introduce foreign agents into drinking water supplies, which became a “barrier to adoption”. There were also uncertainties around the commercial model at the time. 

But the company confirmed that it remains interested in fibre optics for leak detection and is monitoring developments in the market.

Now, a company in Belgium and a project currently in its second phase in England are helping to realise fibre optics growing potential for leak detection.

The Dark Fibre project, led by Severn Trent Water

Laying fibre optic cables for leak detection can be disruptive, but what if the cables have already been laid, or are planned to be laid by other operators?

This is the method favoured by the Dark Fibre project, a collaboration led by Severn Trent Water, with partners including Costain Group plc, Welsh Water, Focus Sensors, Northumbrian Water, Hafren Dyfrdwy Cyfyngedig and South Staffordshire Water.

By using fibre optic strands that are unused by existing telecommunication cable networks running alongside water mains, the project was able to demonstrate the ability to detect leaks and monitor the associated creation of voids and damaged sewers. The fibre optic cables effectively act as sensors that can ‘hear’ leaks across longer distances than current technologies.

The project involved a two-phase trial, the first involving the detection of seven different simulated leak types. The second part of the trial involved a live environment, with installation on a main road. In this part of the trial, two types of leak detection were monitored: Direct detection of nearby leaks by picking up sounds in the fibre; indirect detection by monitoring changes in the saturation of the ground around the fibre cable.

The project demonstrated direct measurement of leaks within a range of +/- 0.5m from the fibre, and an indirect detection range of up to 5m. The success of the pilot led to an award of £1,332,205 from the Ofwat Innovation Fund to carry on the work.

Dark Fibre 2 

Dark Fibre 2 will expand the scale of the original trial, with the aim of proving detection works at longer distances. This phase will monitor 200km of networks using five fibre sensors, as opposed to the 40km monitored originally.

Talking to Talking to Water Magazine, Keiron Maher, innovation architect at Severn Trent, said: “Dark Fibre sensing has the potential to change the industry, by utilising inactive cables already laid, making the whole process faster than ever before.

“Dark fibre leak detection is an emerging technique, proven to have great potential for the water industry. This project will test its capability in the field and develop tools to determine the likely coverage of the system.”

Fluves’ Dali system in Belgium and Netherlands

In Belgium, fibre optic provider Fluves and piping specialist Vigotec have developed a monitoring system called Dali, which has already been used in several European countries.

Fibre optic cables inserted into pipes are connected at one end to a distributed acoustic senor which sends out laser pulses to create a ‘map of reflections’ covering up to 70km of the network. Any vibrations in the network creates a disturbance in the map and those signals can be sent in real-time for further analysis.

Speaking to Civil Engineer, Fluves project manager Thijs Lanckriet explained that the company has developed software that can interpret the disturbances using algorithms, revealing whether they are leaks or some other activity.

Belgium company Farys has been using the system to detect small leaks in its 660km network of pipeline serving over 1 million people. The ability to continuously monitor for potential leaks means that small leaks can be located and fixed before they potentially become problematic.

With many utilities dealing with an ever-ageing network pipes and equipment, the ability to pinpoint emerging leaks is an attractive option. Dutch water company’s Evides and Vitens have been trialling Dali for that very reason, to detect small leaks that might not otherwise affect pressure but that over time will amount in significant losses.

Further considerations

There is more to be done, however, in understanding how best to use fibre optic technology and how to adapt it for different operational requirements.

Claire Fenwick, managing director of infratech services and fibre sensing technology company, Nuron, told Aquatech Online: “People are putting cables in, on or near water pipes and seeing what they can see rather than approaching it the other way round.  Start from the pressing problems, understanding the business case and then designing and integrating the right system to deliver the measurements to the right resolution and cost base.” 

She added: “Fibre sensing works, that is not in doubt, which interrogator, what cable/sensor, where you put it, how it is coupled and how easily it can be installed is what makes the difference.”