Water Leak Detection: The Inside Story

31 March 2016

Each day, the world’s leaky water infrastructure loses billions of gallons of water before it can reach its destination.

The good news, however, is that much of the loss can be prevented by available leak-detection systems. Such systems often rely on equipment located outside of water pipes. But some companies say leak detection is more effective when it’s an inside job.

One such company is Pure Technologies Ltd., a provider of leak-detection services based in Calgary, Alberta, Canada. Pure uses acoustic sensing technology to detect leaks from the inside of pipes.

In conventional leak-detection processes, acoustic sensors located outside the pipe listen for leak noise. These external sensors can have difficulty picking up leak sounds because of ambient noise, large pipe diameters and pipe materials that may be poor transmitters of sound.

Internal Tech Emerges

Thus, the emergence of internal--or inline--leak detection technologies. Inline leak detection systems rely on a sensor inside the pipe that passes over or close to leaks. Inserted into a pressurized pipeline through a tap or an existing access point, the sensor listens for leaks as it is propelled through the pipe by the flow of water. Inside the pipe, the acoustic sensor is not affected by pipe material or diameter.

Inline leak detection might be the only option for inspecting pipes in hard-to-access locations such as under railroads or rivers. It also may be useful in urban areas, where background noise can make it difficult for external acoustic sensors to hear leak sounds.

Pure has developed two products for inline leak detection. One, called SmartBall, rolls along the bottom of pipes. As it rolls through a pipe, SmartBall detects leaks with a hydrophone, which is a microphone designed to listen for underwater sounds. SmartBall’s hydrophone can detect leaks as small as 0.003 gallons per minute in pipes made of any material, according to Pure. In many cases it can locate a leak to within 6’ of iits actual position.

In addition to the hydrophone, key components inside SmartBall’s 2”-diameter aluminum core include a battery, a 4 GB memory card that records leak data and a magnetometer that keeps the ball rolling. Outside the core is a foam shell to suppress SmartBall’s own rolling noise so it doesn’t interfere with leak detection.

SmartBall has inspected pipelines up to 30 miles long, the company says. During its journey through a pipe, the device emits a noise every few seconds so it can be tracked by above-ground sensors and eventually retrieved.

Leashed Detectors

Only when SmartBall is retrieved can its data be accessed and analyzed. But that’s not the case with a tethered inspection device, which is attached to a cable that carries inspection data back to the operator.

This type of real-time inspection tool includes a closed circuit television (CCTV) camera that allows operators to visually assess internal pipe conditions. Although the device is propelled in the direction of the water flow by a drag chute, operators can use the attached cable and a winch to control its motion. For example, they can move the device back and forth to confirm a suspected leak’s location, or to position the device over corroded areas and other points of interest.

Like SmartBall, Pure’s tethered inspection device, called Sahara, uses a hydrophone to find leaks in pressurized water pipes made many materials. But Sahara can locate leaks to within 1.5’ of their actual location, according to Pure.

A fiber optic cable enables both sensor data and CCTV images to be available immediately to operators. One possible drawback is that the attached cable limits the range of the Sahara, which is normally used for pipeline inspections of a mile or less.

Neither SmartBall nor Sahara is sold to utilities. Instead, Pure sends out crews that use the systems to conduct inspections at customer sites.

Sound Alternative

Another inline technology aims to eliminate many of the problems associated with acoustic systems and other conventional leak-detection options. In addition to ambient noise and pipe-related problems, this list includes poor repeatability and reliance on operator or third-party data interpretation.

The tethered Electro Scan probe emits electricity inside a pipe to detect leaks.This alternative to conventional detection technologies takes advantage of the fact that many pipe materials (plastics and concrete, for example) are poor conductors of electrical current. Therefore, a pipe-wall defect that leaks water will also likely leak electrical current.

The system used by crews dispatched by Sacramento, Calif.-based Electro Scan Inc. uses electricity to scan pipe interiors for defects. The system includes a parachute to pull a probe through pressurized water pipes. A fiber optic cable sends data to operators and allows them to reel the probe in.

The probe emits a ring of low-voltage, high-frequency current inside a water pipe. If there are no leaks in the pipe wall, the electricity remains contained within the pipe. If there is a leak, however, the electricity escapes and follows the water to ground. Once outside the pipe, the AC current is conducted by the earth to a ground stake at a base station established by the Electro Scan crew. As a result, the technology is known as “low-voltage conductivity.”

The Electro Scan system determines the size of a leak by measuring how much electricity is escaping from the pipe. The larger the amount of electrical flow, the bigger the leak. It also provides an estimated leakage rate for discovered defects based on in-pipe pressure readings taken by a sensor in the probe.

In addition to the pressure sensor, the probe includes a low-voltage conductivity sensor that finds leaks and determines the flow through them. A CCTV camera helps operators guide the probe and assess interior pipe conditions.

Results in 10 Minutes

Electro Scan claims its system locates and measures leaks less than 10 minutes after a scan is completed. Scan data is transmitted from the probe to a computer in the inspection crew’s van, which displays readings in real time for field operators. Data is also exported to the cloud for processing. The leakage reports provide “repeatable and unambiguous” results that require no operator or third-party interpretation, according to Electro Scan.

As for limitations, low-voltage conductivity only works if the pipe material does not conduct electricity. In addition, Electro Scan’s technology is currently limited to pipes no larger than 16” in diameter. Within the next year or two, the company hopes to expand the range of its system so crews will be able to scan larger pipes, says Mark Grabowski, Electro Scan’s vice president of operations.

On average, U.S. cities are only billing for about 80% of the water that leaves their utilities, Grabowski says. But Electro Scan’s system could cut those losses to the range of 8-10% range. “That may not seem like a lot,” he says, “but in a larger system it adds up quickly over time.”