By Jay Landers

Each year, drinking water systems in the U.S. and Canada experience about 260,000 water main breaks, incurring an estimated $2.6 billion annually in maintenance and repair costs, according to the results of a new survey of more than 800 U.S. and Canadian water providers.

For drinking water utilities, distribution systems are often their longest-lasting – and most expensive – assets. As a result, water providers can face financial challenges when it comes to replacing water mains before they begin to fail. Unfortunately, these costs could be poised to rise in coming years.

Nearly 20% of installed water mains in the U.S. and Canada are beyond their useful lives and have not been replaced because of inadequate funding, according to the same survey, the results of which appear in a recently released report from Utah State University. All told, an estimated $452 billion is needed to cover the cost of replacing the aging mains, the report concludes, a staggering sum that points to the need for greater use of asset management programs within the water sector.

Largest study to date

Dated December 2023 but released by USU’s Utah Water Research Laboratory in late February 2024, Water Main Break Rates in the USA and Canada: A Comprehensive Study summarizes the findings of a basic survey of 802 water utilities within 49 U.S. states and all 10 Canadian provinces. The participating utilities serve more than 30% of the population of the U.S. and Canada and represent nearly 400,000 miles of water main pipe, or more than 17% of the estimated 2.3 million miles of water mains in the two countries. Of the participating water utilities, 172 provided additional information by responding to a more detailed survey.

The study builds on two previous water main studies conducted by USU in 2012 and 2018. In terms of size and scope, the new study is the largest by far, lending it greater accuracy and statistical validity than its predecessors. “The sample size for this study is almost three times larger than the previous 2018 USU water main break study,” the report notes. “In terms of pipe mileage, this is the largest study in the U.S. and Canada of its kind. Previous studies have been based on much smaller sample sizes and consequently may have reduced accuracy in data reporting.”

Among utilities responding to the basic survey, 75% have 500 miles or fewer of water mains. Another 17% of respondents have 500 to 1,500 miles of water mains, while 5% have 1,500 to 3,000 miles. The remaining 3% have more than 3,000 miles.

As was the case with the 2012 and 2018 reports, USU researchers did not ask survey participants about pipe problems associated with joint leaks, construction damage, or tapping of service lines. This decision reflects the fact that the study is “trying to focus on the longevity and the durability of pipe materials over time,” says Steven Barfuss, P.E., M.ASCE, a research professor in USU’s civil and environmental engineering department and an associate director at the Utah Water Research Laboratory. “Data received from utilities about the percentage of total construction failures related to a particular pipe material are presented separately in the report.”

The cost of aging infrastructure

Overall, 19.4% of water mains, for a total of 452,000 miles, “were reported to be beyond their useful lives but have yet to be repaired or replaced due to lack of funds,” according to the report. This figure represents an increase from previous studies. “In 2012 and 2018, the percentages were 8% and 16%, respectively,” the report notes.

The fact that nearly half a million miles of water mains need to be replaced but cannot be because of inadequate funding is concerning, Barfuss says. Assuming a replacement cost of $1 million per mile, USU researchers arrived at the aforementioned $452 billion estimate to replace existing water mains that have exceeded their useful lives.

Meanwhile, the average age of failing water mains was found to be 53 years, according to the report. The study estimated that 33% of water mains in the U.S. and Canada, constituting approximately 770,000 miles, are more than 50 years old. “This aging infrastructure is catching up with itself,” Barfuss says.

The study also found that “43.5% of utilities do use some form of regular condition assessment of their water mains,” the report notes. “This highlights the need for pipe performance data and pipe condition assessment as part of a cost-effective asset management program.”

With its comprehensive breadth and detail, the USU report represents a “great asset management tool for utilities to assess the performance of various piping materials in their systems,” says Bruce Hollands, the president and CEO of the Uni-Bell PVC Pipe Association, which provided partial financial support for the study.

Break rates decrease

On the bright side, overall annual break rates decreased by about 20% between 2018 and 2023, as measured by the number of breaks per 100 miles of pipe per year. Whereas the 2018 study found 14.0 breaks per 100 miles annually, the 2023 study found 11.1, according to the report.

However, this decline in the break rate might simply reflect decreasing use of pipes made of cast iron and asbestos cement, two materials that have the highest failure rates and are no longer manufactured, Barfuss says.

“That’s one of the reasons why we believe (water utilities) reported overall break rates in 2018 that were higher than they are in 2023,” Barfuss says. In 2018, 41.1% of U.S. and Canadian pipes were made of cast iron and asbestos cement, according to the report, which notes that this figure declined to 33.3% in 2023.

Pipe materials, sizes affect performance

Among the utilities participating in the survey, PVC is the most used pipeline material, at 116,345 miles, according to the report. Other commonly used materials include ductile iron (108,670 miles), cast iron (90,657), asbestos cement (42,365), and steel (11,358).

Among these pipe materials, PVC was found to have the lowest annual failure rate, at 2.9 breaks per 100 miles, according to the report. By comparison, the annual failure rates per 100 miles of pipe for the other materials assessed by the study were 5.1 for ductile iron, 9.2 for steel, 10.3 for asbestos cement, and 28.6 for cast iron.

Corrosive soils appear to play a key role in contributing to failures in ductile iron pipe. “Analysis of soil corrosivity shows that ductile iron pipe in highly corrosive soil has over six times the break rate of ductile iron in low corrosive soil,” the report states.

Regardless of material, smaller-diameter pipes were found to break more often than larger-diameter pipes. The study distinguished between distribution mains having diameters of 3-12 inches and transmission mains having diameters of 14 inches or more. “Overall distribution main failure rates at 13.3 breaks (annually per 100 miles) are 505% higher than for transmission mains at 2.2 breaks,” the report notes. At the same time, the report shows that water main break rates are not correlated to utility size.

Although the precise reasons that smaller pipes are more likely to break remain unclear, Barfuss thinks it could have a lot to do with the greater attention that larger transmission mains typically receive. “I truly believe it comes down to the care utilities provide to those transmission lines,” Barfuss says. “They just can’t afford to have those break.”

This article is published by Civil Engineering Online.