Reduce Non-Revenue Water and Prioritize Water System Repairs and Replacement without Breaking the Budget
By: Marc Bracken
Ongoing budget shortfalls for water infrastructure spending is a significant concern among utilities across the United States that are faced with water leaks and main breaks, which are steeply increasing in frequency as years of unchecked deterioration take their toll on pipes that, in places, dates back to the second half of the 19th century.
In February 2011, news outlets across the country reported that Kansas City, Mo., experienced 467 main breaks that winter alone—a 73 percent increase in the number of breaks the city experienced during the winter of 2010. Montgomery and Prince George’s County, Md, which deliver water to 1.8 million people, also made news headlines for breaks in their water systems. According to one article, both counties set a record in December 2010 for having the largest number of water main breaks in a single month—647. The following month, Prince George’s County experienced a 54-inch water main break that damaged nearby businesses and leaked an estimated 50 million gallons of water. As a result of these and similar news headlines, which draw attention to only a very small fraction of the 700 water main breaks that occur across the U.S. on a daily basis, it is no surprise that 15 – 30 percent of treated potable water lost is lost through leaky pipes. The International Water Association defines this “lost water” as non-revenue water (NRW)—treated water that is lost before it reaches the customer. According to the American Water Works Association, such losses cost public water systems approximately $2.8 billion in yearly revenue.
In light of utilities’ continuing budgetary concerns, how can they afford to reduce NRW if traditional leak testing and pipe condition assessment methods have questionable accuracy and can entail the expensive and disruptive process of excavating water mains or pressurizing water systems to expose leaks?
Fortunately, cost-effective NRW reduction is possible as advancements in acoustic leak detection and pipe condition assessment methods can help utilities detect leaks and prioritize water system repairs and replacement—without breaking ground or disrupting service.
These new methods rely on measuring how quickly an acoustical signal is transmitted along a section of pipe, using vibration sensors, and acoustic correlators. The process is completely non-invasive; devices are attached to a section of pipe using standard appurtenances such as valves, hydrants, or direct attachments to the pipe’s outer wall.
An acoustic signal is induced into the pipe and changes to the signal—specifically changes to its transmission or propagation velocity—can be related to changes in the pipe wall structural integrity. This yields a highly accurate measurement of the remaining (or effective) structural integrity of selected pipes while simultaneously detecting and locating leaks. And, due to advances in the sensor design and signal processing technologies, significant improvements have been made in the ability of the system to resolve leak noise in the presence of ambient background noise often created by running water, traffic or pumps. Utilities can therefore detect leaks and assess the condition of pipes of all sizes and materials—including ductile and cast iron, concrete, plastic and asbestos cement—as well as pipes that are located in noisy, high-traffic environments.
The use of such technology is increasing among water service providers across North America, and in Europe, South Africa, Singapore and Australia because of its accuracy and cost advantages over traditional methods.
A recent example is The Sewerage and Water Board of New Orleans (SWBNO). SWBNO has been using acoustic leak detection for perhaps two decades; however, in early 2011 it incorporated recent non-invasive acoustic technology developments into its water loss management and water pipe integrity assessment initiative. During a pilot project that tested the accuracy of the technology, water main leaks that were causing between 75,000 and 100,000 gallons of NRW per day (300,000 - 400,000 liters per day) were quickly located; the amount of water loss was equivalent to filling approximately one Olympic swimming pool every six days.
The Las Vegas Valley Water District has taken a similar approach. While it has a relatively young water infrastructure that experiences very few main breaks per mile as compared to other major utilities, some of its pipes have started to fail more often due to corrosion and other factors. A particularly troublesome section of pipe was part of a 6.5-mile span of 16- to 36-inch mortar-lined, steel cylinder pipeline that ran underneath some of the city’s most popular thoroughfares. The pipe was installed in the 1950s without any cathodic protection or corrosion control and experienced three main breaks over a five-year period. LVVWD expected to have to replace the entire 6.5-mile span of pipe—a major expense that it estimated would cost as much as $300 per foot and would disrupt busy roadways. However, using non-invasive acoustics, the entire 6.5-mile span of pipe was surveyed in only two weeks and LVVWD found that the majority of the pipeline was still in good structural condition, as it contained more than 95 percent of its original wall thickness. Rehabilitation money was therefore prioritized to the areas with the greatest need.
While constrained budgets continue to present difficult challenges for utilities, they do not have to place their efforts to reduce NRW and prioritize water system repairs and replacement on hold. Recent developments in non-invasive acoustics can provide utilities with the ability to cost-effectively and efficiently locate leaks and measure the wall thickness of pipes in their water systems without having to undergo the expensive and time-consuming processes typically associated with traditional leak detection methods.
Marc Bracken is vice president and general manager of Mississauga-based Echologics, a leading developer and provider of acoustic-based technologies for water loss management, leak detection, and pipe condition assessment, and has more than 18 years of experience in acoustical and vibration engineering.