Science Video

Stopping Sinkholes
Engineers Design Sensor That Detects Leaky Pipes From The Inside

October 1, 2007 — Engineers can now drop an acoustic sensor into working water pipes and detect leaks, as small as one quart per hour. The sounds created by holes are pinpointed, leading to earlier detection, patch repairs, and, of course, less lost water. The system can also map water systems, something that has not been accurately done in some areas.

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We all watched the pipes burst underground in New York City. In fact, the National Research Council issued a report saying much of the nation's water distribution system will need to be replaced in the next 30 years.

To replace all those pipes would cost billions of dollars. Instead of replacing them, what if you could just fix the problem spots? But locating those spots is the tricky part. In the United States, just beneath our feet, lie more than one million miles of pipes that bring us water.

"Almost every day, in any given city, anywhere in the states or North America, there is going to be a pipe failure," says Brian Mergelas, Ph.D., physicist at the Pressure Pipe Inspection Company in Toronto.

When those pipes leak and fail, sinkholes, floods, even geysers can happen. Now, Mergelas has a solution.

"This is the only system in the world for looking at leaks in large diameter pipes," he explains.

It's called the Sahara system. Engineers drop this probe into working water mains. The flowing water catches an attached parachute and pulls the probe through the pipe. The probe picks up the unique sound created by a leak ... no matter how small.

"Someone will be listening in real time to the sounds that we are hearing inside the pipe," Mergelas says.

Then, the probe sends out a signal, indicating the exact location of the leak.

"In the states, there are about 5,400 water utilities, and so every one of those utilities could benefit from this," Mergelas says.

Instead of replacing whole mains in aging pipe systems, utilities can simply fix the problem spots, saving money and saving millions of gallons of water that would otherwise be lost.

"These are all hidden leaks. So we are finding them in time for them to actually be proactive to do something about it," Mergelas says.

Right now, 40 cities across the U.S. are proactively managing their pipes with the new system. The system is designed to locate leaks in pipes that are 12 inches in diameter or larger. The system will locate three leaks per mile in any given pipe line.

The American Waterworks Association contributed to the information contained in the TV portion of this report.

BACKGROUND: Engineers are using the tether-controlled Sahara sensor inside water mains to pinpoint even the smallest leaks - without disrupting pipeline service. Consumers can't see the technology but the nonetheless reap the benefits: the sensors ensure that water keeps flowing through pipes reliably and safely.

HOW IT WORKS: The system is inserted into a live transmission main through any tap two inches or more in diameter. It is safe for all drinking water systems. The probe is carried along the pipe by the flow of water, and the system locates leaks as small as one-quarter of a gallon per hour. It does this, in real time, through the identification of distinctive acoustic signals generated by leaks in the pipe walls, the joints, or steel welds. Once a leak has been detected, the sensor head can be stopped at the precise position of the leak. Its location within the main can be identified from the surface and accurately marked for subsequent excavation and repair. As a result, operators can also use Sahara to accurately map the course of a pipeline.

BENEFITS: Depending on the pipe configuration, lengths of up to 6000 feet can be surveyed with a single insertion, and inspections can be conducted in mains with a diameter of at least 12 inches. The ability to identify individual leaks has many benefits, such as helping water transmission pipeline operators pinpoint the exact location of the leaks causing a pipeline to fail a pressure test. Based on this information, it is easier to establish priorities for repair and replacement of parts. More generally, being able to establish the structural integrity of a given water transmission main makes it easier to more accurately value pipeline assets, and comply with legal requirements.

SENSING ABILITY: A sensor is a type of transducer: an electronic device that converts energy from one form to another. For instance, microphones convert sound waves into electrical signals, while speakers receive the electrical signals and convert them back into sound waves. There are many different kinds of sensors, but most are electrical or electronic. Microelectro-mechanical systems (MEMs) integrate electronic and moving parts onto a microscopic silicon chip, making them ideal for new sensor technology. The term MEMS was coined in the 1980s. A MEMS device is usually only a few micrometers wide; for comparison, a human hair is 50 micrometers wide. Among other everyday applications, MEMS-based sensors are used in cars to detect the sudden motion of a collision and trigger release of the airbag. They are also found in ink-jet printers, blood pressure monitors, and projection display systems.

Note: This story and accompanying video were originally produced for the American Institute of Physics series Discoveries and Breakthroughs in Science by Ivanhoe Broadcast News and are protected by copyright law. All rights reserved.