This story was originally published in Public Works.
The oldest university-based water research facility in the U.S. presents "Water Main Break Rates In the USA and Canada: A Comprehensive Study," an update of a 2012 study by Buried Pipe Design author Steven Folkman, PE. Head of Utah State University's Buried Structures Laboratory, Folkman gathered information from 300 utilities with 200,000 miles of installed mains serving 52 million people, which represents 14.5 percent of the population of the U.S. and Canada. As one of the largest surveys on this topic, the report's results can help in revising pipe service life assumptions used in the past.
Here's how the 23,803 pipe failures that required repair break down:
Break rates have increased 27 percent in the past six years.
Break rates for cast iron and asbestos cement pipes, which together represent almost half of the installed water mains in North America, have increased 46 percent and 43 percent, respectively, since 2012. Together, CI and AC pipes are mostly responsible for the spike in pipe failures.
Cast iron pipes represent the largest pipe material inventory and 82 percent are over 50 years old.
Cast iron pipe in high-corrosion soil has 20 times the break rate than one in a low-corrosion environment. Ductile iron pipe in high-corrosion soil has 10 times the break rate.
Polyvinyl chloride (PVC) pipe has the lowest overall break rate when compared to cast iron, ductile iron, concrete, steel, and asbestos cement.
Construction-related failures were equivalent for both PVC and ductile iron pipes, pointing to the need to improve practices for installation, location services, and inspection.
Smaller municipal utilities have twice the break rates as larger utilities.
The percentage of water mains beyond their useful lives has doubled from 8 percent to 16 percent.
The percentage of water mains over 50 years old has increased from 22 percent to 28 percent in the past six years.
An average of 0.8 percent of pipe is replaced each year. This equates to a 125-year national pipe replacement schedule. Replacement rates should be between 1 percent and 1.6 percent, equivalent to 100-year and 60-year replacement schedules, respectively.
Pipe material usage varies significantly over geographic regions, suggesting selection is based on historical preference vs. comparative cost analysis or environmental conditions.
Average pressure fell to 69 psi from 77 psi in 2012, which is well below the maximum operating pressure of water mains, extending pipe life as well as reducing leaks and breaks.
Estimated average water loss due to leakage is 10 percent.
To view the full report, click here.
This study contributes to the continuing efforts of EPA's Aging Water Infrastructure research, Virginia Tech's Sustainable Water Infrastructure Management Program, U.S. Conference of Mayors' Water Council, and the asset management and water infrastructure condition assessment efforts of the American Water Works Association and American Society of Civil Engineers.
"This report provides greater insight into the drivers of the aging water infrastructure crisis and offers data utilities can use to benchmark pipe material performance. It will be a valuable asset management planning tool for water utilities," says Folkman.
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