Underwater microphones developed by the Royal Navy to track down enemy submarines are being used by Yorkshire Water to detect leaks.

The firm claims to be the first water company in the world to use hydrophones accurately to pinpoint water leaks in large diameter pipes over long distances and the equipment was tested in Bradford.

The technology was first developed by scientists at the Ministry of Defence to help Naval destroyers hunt down enemy submarines.

Hydrophones are used by water companies around the world and work by measuring the length of time sound travels along a pipe between two points.

However, previously it only worked over long distances on small diameter metal pipes because on larger pipes the high frequency sound waves disappeared into the thick walls before they could be measured accurately.

But by working with QINETIQ, an agency linked to the Ministry of Defence's Defensive Evaluation Research Agency, Yorkshire Water adapted the technology to work effectively on large diameter metal mains.

John Procter, principal project engineer with Yorkshire Water, said the ability to pinpoint leaks in this way would mean savings in lost water, time and excavations.

"This is a real breakthrough and gives Yorkshire Water a world lead in the technology," he said.

"It's most satisfying that this technology, first developed for military use, is now helping us in the fight to cut unnecessary loss of water due to hard-to-detect leaks."

Scientists looked at sounds in water and developed a theoretical model.

The theory was then tested on a 36ins diameter main near Bradford - hydrophones were inserted to monitor a 3km stretch which contained a leak.

Signals sent between the two hydro-phones were measured and engineers could pinpoint the leak.

Mr Proctor said: "The results from this method are really encouraging.

"We will be training our engineers in the use of hydrophone technology and are working closely with QINETIQ to develop a range of hydrophones that can be used commercially in this industry."