Tackling Non-Revenue Water (NRW) Small Leaks

Small leaks sink big ships – the same can be said for large-diameter pipes in utility networks. While large leaks or ruptures are seen as newsworthy stories accompanied by images of water flowing down the streets; smaller leaks can often be more devastating. Left undetected, they can add up over time, contributing significantly to Non-Revenue Water, and eventually, they too can lead to catastrophic pipeline failures.

Many utilities focus leak detection efforts on locating and repairing large leaks, with less priority being placed on identifying smaller ones. While repairing these large leaks is integral to preventing major failures that are expensive to the utility and disruptive to the surrounding environment; finding and repairing small leaks may present the best opportunity for long-term reduction of NRW loss.

Non-Revenue Water loss in the United States is estimated to be between 14 and 16 percent on average, while some systems are suspected to have revenue loss of up to 40 percent. In developing countries this number is much higher, with NRW loss as high as 65 percent in some areas.

The Benefits of Finding Small Leaks

Identifying and repairing small leaks early in their life may be the best course of action to address the problem of future water loss. Catching a leak while it is small prevents decades of sustained water loss that may not otherwise be detected. Over the years, unreported water loss could mean significant financial loss for the utility. Additionally, utilities that fail to proactively find and fix unreported water main leaks allow a growing backlog of new leaks to occur slowly over time. The result is mounting water loss volumes and “hot spots” in some locations; as a number of small leaks can ultimately lead to a major pipeline failure.

Acoustic leak detection sensors have been developed to run through in-service water trunk mains, bringing the sensor to the leak sound, rather than relying on the leak sound to find the sensor. Inline surveys work exceptionally well on large-diameter water transmission trunk mains, which are often poor at transmitting leak sounds and have limited access points to the pipe.

Inline Leak Detection Case Studies

Inline leak detection services have been proven to reliably identify very small leaks on water trunk mains with pinpoint precision, without requiring the water main to be taken out of service.

Engineering staff from Metropolitana Milanese in Milan were able to reduce their water loss and renew the condition of one of their critical mains by conducting proactive inline leak detection using Pure Technologies’ SmartBall® inline leak detection tool. They found a concentration of eight small leaks in a 240 meter section of pipe, exposing a weak area of pipe that could eventually lead to a critical failure. Metropolitana Milanese was then able to take proactive measures to defend against major ruptures.

SmartBall with case and insertion tools

The SmartBall tool is a free swimming leak detection technology that follows the product flow of the pipeline, picking up acoustic anomalies that identify and locate very small leaks and gas pockets. Because it has very little operational noise, the sizes of the detected leaks are minute. In optimal operational conditions leaks as small as 0.028 gal/min have been detected.

With the ability to detect even smaller leaks at 0.005 gal/min (in optimal conditions), Pure Technologies’ Sahara leak detection platform is another tool that can be deployed. Because it is a tethered system that is operator controlled, it is also able to map the location of the leak within 0.5 meters (3 feet). The Sahara tool simultaneously provides real-time visual inspection of live pipeline conditions thanks to an inline video system that travels along the pipe with the acoustic sensor.

Carried out regularly, comprehensive leak detection programs can not only identify large, potentially catastrophic leaks, but also smaller leaks that over time contribute to NRW and eventually become damaging themselves.

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