Excavations and tests of PVC pipe in service around the world indicate the pipe material can be expected to provide reliable service in excess of 100 years, a new study says.
That's twice as long as some pipe professionals would admit, said Steven Folkman, author of the “PVC Pipe Longevity Report: Affordability & the 100+ Year Benchmark Standard.”
Folkman, a registered professional engineer, oversees Utah State University's Buried Structures Laboratory, where researchers have been analyzing and testing all kinds of pipes for 50 years. Their study released May 14 is based on past dig-up reports, the results of new quality tests, and life-cycle cost analysis.
“Saying how long pipe will last is a little debatable,” Folkman said in a telephone interview. “Talk to a ductile iron guy and he'll say: ‘They haven't proven anything.' The point of my paper is that it just isn't me.
“Here's about 20 other different sources and they are all saying about the same thing. We pulled the information together, including some that we gathered. We're saying here is a mountain of evidence and all of our honest indications are if the PVC pipes are properly produced and properly installed, all the data indicates the longevity is in excess of 100 years.”
USU researchers looked at the performance of PVC pipes used in water systems in Australia, Europe, and North America. Dig-up reports indicated there was no degradation after decades of use.
Some exhumed U.S. pipes installed in 1964, 1987 and the early 1990s also were subjected to mechanical tests at the USU lab in 2013 to assess deterioration during service. The study says all the pipe still meets applicable standards.
“North American studies state that 100 years is a conservative estimate,” the report says of PVC pipe longevity.
In addition, accelerated aging tests conducted elsewhere helped the USU researchers come up with their lifespan estimate. The summary says the study confirms a 100-year benchmark as an industry standard, which the Water Research Foundation also has reported.
Funding for the tests came from the Dallas-based Uni-Bell PVC Pipe Association.
Folkman said the findings are a follow up to a 2012 USU study that showed PVC pipe has the lowest rate of water main breaks compared to ductile iron, cast iron, steel, concrete and asbestos cement.
Looking at cost
Another component of the latest study addresses financial challenges for utilities. More than a million miles of pipe are nearing the end of their useful life. The cost to replace that pipe, coupled with the cost to expand some parts of the water system, will surpass $1 trillion in the next 20 years, according to the American Water Works Association.
The USU study says rate payers are likely to shoulder the expense, so finding the lowest-cost way to complete a replacement project needs to be applied.
“The big take away is when you run the numbers to decide what is the best investment, one of the critical considerations is how long will this pipe last,” Folkman said. “If it's done right, you should be able to base that on 100 years for PVC pipe.”
The study points to a North Carolina city that got cost estimates this year for replacing two water lines with PVC pipe and ductile iron pipe. The price quotes for 1,600 feet of eight-inch pipe came in at $29,588 for PVC pipe and $42,352 for iron pipe. And, the price quotes for 1,500 feet of six-inch pipe came in at $20,125 for PVC pipe and $40,110 for iron pipe.
With pipe needs varying by geography; soil, weather and corrosion conditions; and whether distribution or transmission lines are being replaced, Folkman said everyone needs to crunch all the numbers.
“What makes the best financial sense?” he asked. “The pipe that costs the least and lasts the longest is easily a wise, affordable pipe investment with limited dollars to build infrastructure.”
He figures PVC pipe currently makes up about a third of U.S. water infrastructure and he expects that to grow. However, Folkman said he isn't touting the pipe material as the sole solution.
“There's no one answer,” he said. “You don't do all your pipe in one kind of material. You have very large transmission pipes that might be many miles and they are often steel or concrete. You'll never have one type of pipe.”
The goals of the study were to continue exploring the reliability and longevity of PVC pipe and to support research efforts to address concerns over water service sustainability and affordability.
“It's hard to come down and say clearly PVC pipe is the answer,” Folkman said. “It's like saying who makes the best car? Simply put: This is a quality product and you shoud expect it to last in excess of 100 years if you install it correctly.”
If a pipe fails in less than 100 years, the study says it either has a manufacturing defect, was installed improperly, is part of a poorly designed or maintained system, or was the wrong material selected.