Southern Water is trialling technology developed by Lightsonic that repurposes Openreach's fiber-optic telecoms network to detect leaks in underground water pipes. The system works by monitoring microscopic changes in light passing through fiber cables, identifying vibrations caused by nearby leaks, and using machine learning to distinguish genuine water loss from background noise such as traffic and roadworks. Southern Water has adopted the technology following an exceptionally hot and dry summer, with much of southern England experiencing drought conditions, and aims to strengthen its drought resilience and meet regulator Ofwat's leakage-reduction targets for 2030.

Lightsonic's technology is already preventing the loss of more than four million litres of water daily across 650 kilometres of the UK's water network, according to the company's claims. The trial builds on earlier successful testing by Openreach and Affinity Water in March. Southern Water, which serves Hampshire, the Isle of Wight, West Sussex, East Sussex, and Kent, has already reduced leakage for three consecutive years and views this technology as a means to accelerate leak detection and repair. However, the company's water conservation efforts are overshadowed by recent enforcement action: it faces a £2.4 million fine for pollution incidents in Kent and a previous £7.1 million penalty for illegal sewage discharges that closed beaches in Thanet.