Las Vegas Water District serviceman Mike Bailey uses a device called a "correlater" to listen for leaks in a pipe beneath Grandbank Drive on Thursday. Bailey was directed to the area by a remote leak-detection device that "heard" what it thought could be a leak there. None was found. Photo by Clint Karlsen.

Forget the National Security Agency. When it comes to electronic surveillance in Las Vegas, the most expansive spy network might just belong to the water company.

Over the past two years, the Las Vegas Valley Water District has installed 8,000 high-tech listening devices beneath streets across the valley.

But instead of the chatter of al-Qaida operatives, the water district is hunting for the telltale sound of leaky pipes.

So far, the $2.1 million remote-listening program is credited with identifying nearly 600 leaks that utility crews might not have known about otherwise. By patching those leaks, the district estimates it has been able to halt the loss of more than 575 million gallons of water, enough to supply about 3,200 households for one year.

The devices also have saved the district money and time by finding smaller leaks before they could grow into major problems.

"Our goal is to keep the water in the pipes," said Kevin Fisher, director of operations for the water district. "It's apparent this system has paid for itself."

The listening devices look like a cross between a travel coffee mug and a walkie-talkie and are run by a battery built to last at least five years. They have powerful magnets in their bases so they can be attached to underground pipes.

Las Vegas was the first city in the country to apply the technology systemwide.

Fisher said the water district became sold on the technology after trying out a few of the units in 2003.

"We did a test drive," he said. "Much to our surprise, we did detect some below-surface leaks we did not know about."

Remote leak-detectors now cover some 3,000 miles of pipeline, which represents about 90 percent of the water district's distribution network. The 8,000 units are spaced about 500 feet apart to listen for sustained vibrations that might indicate leaks.

Each device lies dormant for most of the day, then comes alive for five minutes at 2 a.m., when most people are asleep and the water distribution system is at its quietest.

If a sensor detects any unusual noise, it will wait an hour and then listen again.

"It looks for consistent sound over a long period of time," Fisher said.

The water district employs four people to drive around the valley with receiver units and download data from each listening device.

It takes the crew about six weeks to check all 8,000 devices.

Tom McGee is director of operations for Fluid Conservation Systems, the Ohio-based company that developed the Permalog leak-detection devices the water district is using.

Before the advent of what he calls "proactive leak detection," McGee said, utility workers had two choices: wait for leaks to grow large enough to show up at the surface or go out and listen to the pipes themselves.

"For a city like Las Vegas, that could take five years," McGee said. "Every neighborhood in the city is being checked a couple times a year instead of once every five years. The real benefit to this is time."

"That's what's neat about this (technology). It's always watching," Fisher said.

McGee said some 170,000 Permalog units are in use around the world, about 40,000 of them in the United States.

"Here, this is still in its infancy. There's a lot of cities waiting to see what happens," he said. "It's mostly catching on in the Southwest first, because they're in the biggest crunch. They not only have a financial interest, they have an environmental interest."

El Paso, Texas, employs the nation's largest network of remote leak-detectors, with 11,000 devices deployed across about 80 percent of its pipeline network.

The remote sensors are credited with saving about 6 million gallons of water a day for the border city of about 715,000 people.

"They work extremely well," said John Balliew, water systems division manager for El Paso Water Utilities.

McGee said water utilities in Denver and Phoenix and several of its suburbs have begun to experiment with "proactive leak detection."

Under ideal conditions, the Permalog system can "hear" a leak as small as one gallon per minute on an underground pipe up to 1,000 feet away, McGee said.

The water district can use what it learns from the listening devices to help them decide which parts of its aging system to replace first, he said.

"It's kind of giving them X-ray vision. They can see underground," McGee said.

Fisher said the water district plans to spend another $142,000 on a different style of leak detection unit for the water system in Kyle Canyon on Mount Charleston, where the soil is gravelly and leaks often do not surface.

"We're fixing leaks on our side of the meters, just as we'd hope our customers would on their side," Fisher said. "It's all part of conservation."