The Many Ways to Pinpoint Water Leaks

From leak detection and locating to correlating and logging, here’s a breakdown of the tools that can help you serve your utility customers' water loss management efforts

The Many Ways to Pinpoint Water Leaks

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There are a number of different technologies and tools that can aid a utility's water loss management, each with its advantages and limitations.

In most cases, you can and should use more than one tool. Just as a doctor might use an X-ray, a CT scan machine, Ultrasound, or MRI to find hidden flaws in a patient's body, you can use a number of different technologies to find flaws in a distribution system, with each piece of equipment using a slightly different method or working better than others in a specific situation.

Here are a few of those tools and what they offer toward the goal of water loss management:

Leak Detection

Leak detection is the simplest form of water loss management. All it is is discovering that there is, in fact, a leak. You can't fix a problem until you know that there is one.

Passive leak detection is when a utility just sits back and waits for the public or its staff to report water coming up where it shouldn't be. Hopefully, a utility is a bit more proactive. Not all leaks will be evident on the surface as they may leak into streams and rivers, back into the ground or an aquifer, or into storm or sanitary sewers unseen. One form of leak detection is comparing the amount of water produced to the amount of water sold through metering to come up with a figure for “non-revenue water.” A portion of non-revenue water will commonly be used for fire protection or come from inaccurate metering, but if the difference is large or starts to rise, that would be a sign that there are leaks developing somewhere in the system.

Now the utility needs to find out where they are to fix them. Leak detectors can be used to listen to waterlines for leak noise at hydrants, valves, or meters. Again, this can tell you that there is a leak, but it does not necessarily pinpoint the exact location needing repair. That's where a contractor like yourself may come into the picture, as you need equipment to physically locate the problem.

Leak Locators

Leak locators can be simple or technically sophisticated, but in both cases they are tools that can help you find the location of known or unknown leaks in the distribution system. Water doesn't always come up exactly where the leak is located, particularly when under pavement. A combination audio leak detector/leak locator can be used to detect the sound of leaks on a water main at access points, then follows the lines on the ground above the pipe to hone in on the maximum sound as a leak locator.

Leak locators normally put some numeric value to leak noise so that you know when you are getting closer to the leak. They can be very simple analog devices with no more than a ground microphone and earpiece. Better leak locators will have high-end leak noise sensors with digital audio processors that can filter out background sound and loud noises. This helps the worker more accurately differentiate leak sounds from non-leak sounds, even in noisy environments. It also helps detect what type of leak it is, such as a main leak versus a service line leak, or a pinhole leak versus a large crack. A limitation of devices that locate the leak noise from the ground over the pipe is that you must know where the pipe is underground to listen on top of it. You need to have accurate GIS, maps, markings or a pipe locator as well.

Leak Noise Correlators

A leak noise correlator can be used to mathematically determine where a leak is located between two leak sensors, and can quickly and precisely pinpoint a leak. Leak sound will travel down the pipe wall away from the leak. Engineers have determined the normal speed of sound through different sizes and materials of pipe. These speeds are programmed into software so that a mathematical formula is used to determine the time difference leak noise takes to reach two or more sensors from the point of the leak.

Three things are generally needed to do the calculations: the pipe material, pipe diameter, and the footage of pipe between the sensors. With these inputs, the software can accurately calculate the distance of the leak from each sensor. Leak correlators can give very accurate leak locations, and can often even find multiple leaks in the distance between the sensors at one time. A best practice is to double-check the correlation by verifying the location of the leak with a ground microphone in case there were errors in the data entered.

Leak Loggers

So far, all of the items discussed are used live in the field by a person. However, many leaks are difficult to find in daytime hours due to traffic, noise from the everyday use of the water system, lower system pressures due to use, and other factors. Leak loggers take leak detection and locating to the next step by being able to log leak sound without a worker present, which could be at night or on weekends. Logging can also be used to take repeated leak noise recordings over time to determine if a leak is growing, developing, or to rule out high short-term usage that could be falsely detected as leak. Leak loggers can record leak sound at a single location like a simple leak detector. Leak correlators that can be set to log and correlate at the same time can also be used.

Another type of leak logger is a permanent or semi-permanent logger. These loggers can be installed in quantities of a few or even thousands in valve boxes and left for a week or two to survey and monitor an area, or on a permanent basis throughout the distribution system. When permanently installed and read with a drive-by system, they are proactively monitoring for new leaks 365 days a year. They can catch leaks when they start small, reducing the total water that is lost. Since many leaks start small and grow over time, they can often leak for weeks or months before actually being detected visually. Since smaller leaks are easier to handle, this is beneficial to a utility.

Leak Mapping

This is a newer concept of recording the location and other data from leaks in a geographical format, typically integrating with GIS systems or a geo-database. This can build an information database on leaks and water losses to predict weak areas for leak surveying, plan pipe replacement and rehabilitation, cost-justify line replacement for a utility's budget, and begin to learn what may cause certain types of leaks in different areas or different types of pipes. Keeping a history of leaks and repairs can be valuable information in managing a water system and planning to prevent future losses.

Mapping leaks allows visualization of the system leak history as a whole. Data for a leak mapping system can come from work order systems, manual entry, or data logged from many different types of leak locating and logging devices. You can also manage a system using sophisticated water loss analytics  software for combining water production and distribution data from a SCADA system, water consumption data from an AMR or AMI metering system, and pipe and logger location data from GIS or other mapping sources.

Whether you're working for a utility that has 100 users or 1 million, there are tools available that will fit all budgets to reduce non-revenue water loss.

About the Author

Mark Beatty is CEO and principal owner at Utility Technologies LLC. This article was originally posted on LinkedIn.



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