NORTH West Water is currently funding three separate research projects into new techniques for detecting underground leaks.

One of them includes Bolton trials of a prototype "hydrophone" due to start this summer.

The hydrophone is a highly sensitive microphone developed by the Water Research Centre which detects the sound of a leak as it travels through the main.

This device, no more than 1.5 inches wide, is attached to a mini "parachute" which carries it through the main with the flow of water.

The parachute then collapses to allow the hydrophone to be pulled back out of the main.

Mr Dave Pearson, leakage manager for North West Water, said: "Almost half of all our leaks occur underground and are never visible on the surface, which makes them very hard to find.

"A town the size of Bolton has more than 800 miles of water mains with almost one million joints, any one of which could be leaking."

Tests on the hydrophone form part of North West Water's programme to cut leakage by 250 million litres a day by the year 2000.

The other ideas are:

Cambridge-based scientific consultancy Mecon is working with North West Water to develop a radar so sensitive that it can detect the slightest vibration made by a leaking pipe.

The portable radar will allow water workers to pinpoint leaks as they walk the length of a water main.

work will begin soon on building a prototype of the radar - which will resemble a metal detector - so that field trials can be carried out.

Researchers from Edinburgh University are using thermal imaging equipment to detect leaks on trunk mains.

They fly over the route of the mains, identifying changes in colour or temperature of vegetation which could signify leaking water.

Information is passed back to North West Water.

Mr Pearson says finding the exact source of an undergound leak is a difficult and time-consuming job.

"It can often take a two-man team up to three days to track it down," he said.

Mr Pearson added: "The North West has one of the oldest and largest water mains networks in the country and we are constantly seeking new and more efficent ways of tracking down leaks.

"Perhaps some of this new technology will prove to be the leakage detection method of the future."

Converted for the new archive on 14 July 2000. Some images and formatting may have been lost in the conversion.