Large Diameter Pipelines Do Leak NRW
Although leaks on small-diameter distribution pipelines are the most common form of leak a utility encounters, leaks on large-diameter transmission pipelines are of greater importance in maintaining safe and reliable service delivery. Because large-diameter leaks are less common, they often go undetected for long periods of time resulting in potentially massive water losses.
Most utilities across North America lose between 15 and 20 percent of treated water before it reaches the tap; however, in some municipalities this number is between 30 and 40 percent (U.S. EPA, Environment Canada). The amount of water lost is referred to as Non-Revenue Water (NRW), since the utility is unable to bill for it. To address NRW – which accounts for billions of dollars annually in lost water, as well as energy costs needed to treat and pump the water – many utilities complete leak detection programs.
Although leak detection programs for small-diameter distribution mains can yield a reduction in NRW, programs that focus on leaks on large-diameter transmission mains can produce a more significant reduction in NRW.
A study completed by the American Water Works Association showed that while leaks on large-diameter pipelines make up less than 5 percent of the total number of leaks, they account for more than 50 percent of the total water lost from leaks. This is primarily because transmission mains carry water at a much higher capacity and operating pressure than distribution pipelines. By focusing leak detection programs on large pipes, a utility can achieve a large reduction in NRW by identifying and repairing even one leak on a major pipeline.
With infrastructure aging and reaching the end of its design life across North America, there has been an increase in the number of pipeline failures utilities are experiencing. Although a failure to a water distribution main can be inconvenient and disruptive, large-diameter transmission main failures carry an average cost of $1.7 million; utilities can prevent these failures by managing their most critical infrastructure through leak detection programs. Leaks are often a preliminary indicator that a pipeline will eventually fail, particularly on metallic pipes where corrosion is the main cause of rupture. By identifying and repairing leaks proactively, utilities can reduce the likelihood that a pipeline will fail.
While leaks on large-diameter pipelines make up less than 5 percent of the total number of leaks, they account for more than 50 percent of the total water lost.
With over 2,000 miles of large-diameter pipelines inspected, Pure Technologies has located more than 4,000 leaks for an average of 2.2 leaks per mile using advanced inline leak detection technologies. Locating these large-diameter leaks has significantly reduced NRW, saved millions of gallons of water and helped prevent failures for utilities across North America. Saving Water, Saving Money in the Gwinnett County, Georgia, Department of Water Resources
Olson, Eric W.; Henderson, James C. American Water Works Association / 01-Sep-2007