Openreach broadband fibres find 100+ water leaks in trial with Affinity Water

What happened

Openreach, Affinity Water and the UK sensing firm Lightsonic published results on 12 March 2026 from a trial that turned spare fibres in Openreach's broadband network into a continuous water leak detector. In the first three months of a six-month trial, the system located more than 100 leaks across 650km of Affinity Water's network, saving around 2 million litres of water a day — more than 700 million litres a year, roughly the daily needs of 10,000 people.

The trial ran at five sites across Affinity's supply area in Hertfordshire, Buckinghamshire and Surrey: Walton-on-Thames, Hemel Hempstead, Luton, Chesham and Amersham, and Ware. Affinity Water estimates the avoided abstraction, treatment and pumping is worth up to 140 tonnes of CO2 a year.

The technology

The system uses distributed acoustic sensing (DAS), supplied by Lightsonic. A laser interrogator fires pulses down unused "spare" strands in Openreach's existing fibre cables and reads the backscattered light, in effect converting the cable into thousands of vibration sensors along its length. Water escaping a pressurised main produces a characteristic acoustic signature in the ground; because telecoms ducts and water mains often share the same streets, the fibre picks it up.

Machine learning does the discrimination, filtering out traffic, roadworks and other background noise, and the system can typically place a leak within a few metres. The contrast with current practice is stark: conventional leak detection relies on targeted surveys, loggers and technicians with listening sticks, whereas DAS monitors the whole covered network continuously, 24 hours a day, with no digging and no new sensors in the ground.

James Curtis, Affinity Water's head of leakage, said the technology complements field technicians rather than replacing them, enabling earlier intervention, better planning and less disruption. Trevor Linney, Openreach's director of network technology, said the results show the full-fibre network "delivers value beyond broadband", and noted the same sensing approach can detect gas leaks and monitor bridges and tunnels. Lightsonic chief executive Tommy Langnes said detecting 2 megalitres a day "shows what's possible when fibre sensing and existing infrastructure combine at scale".

Why it matters for UK & Ireland

England and Wales lose roughly 3 billion litres of drinking water a day to leakage, about a fifth of supply, and the industry has committed to halving leakage by 2050. Progress has been slow partly because finding leaks is labour-intensive and reactive: many are only located once water surfaces. A passive sensing grid that already runs down most streets changes the economics of detection.

That is the significant point: the sensor network is already built. Openreach describes the approach as scalable across the UK on its national fibre footprint, and every cable laid for broadband is potentially a leak sensor requiring only interrogator hardware and software at the operator's end.

For water companies facing Ofwat's tightening leakage targets and the costs of the AMP8 investment period, borrowing telecoms infrastructure is far cheaper than instrumenting mains directly. For Openreach and BT, it points to a second revenue stream from an asset built for a different purpose — and the same logic applies to fibre networks in Ireland.

The trial also hints at a broader pattern GridteamAI has tracked elsewhere: infrastructure networks doubling as sensing platforms for one another, with fibre monitoring water, gas and structures rather than each utility building parallel systems.

What to watch

The trial's full six-month results, and whether the leak-location accuracy and false-positive rates hold up as coverage widens. Openreach describes the approach as scalable across its national fibre footprint; the commercial model, who pays whom and under what regulatory treatment, is not yet public.

Watch too whether other water companies sign up ahead of AMP8 leakage commitments, and whether the gas and structural monitoring applications Linney flagged move beyond the drawing board. If they do, spare fibre becomes one of the more quietly valuable assets in British infrastructure.