America Is Replacing Its Pipes: Is Ductile Iron Pipe a Good Alternative for Plastic?
Anthony Wallace | February 26, 2024 | Environmental Health News
Across the U.S., there are more than 2 million miles of water pipes installed beneath our feet and out of sight — and they’re getting old.
According to the U.S. Environmental Protection Agency (EPA), there are 240,000 water main breaks each year and over the next two decades, it’ll take about $420 billion to repair and improve the nation’s water distribution and transmission systems. In addition to aging pipes there are those that pose clear health risks: In 2021, Congress allocated $15 billion specifically for replacing lead service lines. The decision that municipalities across the country will face now is what type of pipe material they should use to replace the old ones.
Plastic pipes, like polyvinyl chloride (PVC), tend to be less expensive than established metallic pipe materials like ductile iron pipe (DIP). In 2017, Bluefield Research, an advisory firm focused on water, projected that up to 80% of municipal investment in water pipes over the next decade could go to plastic. However, there are mounting concerns about toxic material leaching from this type of pipes, further complicating the calculation for municipal decision makers trying to manage the financial, environmental and health impacts of water infrastructure materials.
Like so many communities across the country, owing to its affordability, PVC pipes became a favorite in Prescott, Arizona, in the 1980s.
“Developers decided to use PVC because it's cheap,” Steven Olfers, the city of Prescott’s Utilities Manager, told Environmental Health News (EHN). “It's a cheap capital expense compared to [ductile iron pipe].”
But now Prescott is pulling the plug on PVC. The city’s mayor told residents in a New Years letter that they would use ductile iron pipe going forward for water mains—those are the large pipes that carry water into communities, while service lines are the smaller ones that carry it from mains into homes and buildings. While copper, stainless steel and various plastics are options for builders working on service lines, ductile iron and plastics like PVC are the major options for municipalities considering mains. Prescott’s chief concern for their pipes, Olfers said, was durability.
“We've had a large number of failures on PVC pipes that are fairly new,” he said. “Rocky soils and areas around here just wreak havoc on that stuff.”
The mayor’s letter stated that the city’s cost for ductile iron pipe is $36.00 per linear foot, while PVC is $33.50. In Prescott, that cost is made up for by longevity, the letter stated: where ductile iron typically lasts between 60 and 80 years, PVC only lasts 20 to 30 years.
“I cannot speak for other utilities, but for potable water in non-corrosive soils, ductile is the way to go,” Olfers said. “It offers [a] long life with low maintenance.”
Prescott’s decision to move away from plastic was based largely on their unique geology. Andrew Whelton, a professor of civil, environmental and ecological engineering at Purdue, told EHN that leaders across the country need to consider a myriad of factors like their environment, the makeup of their water and the specifics of the materials they’re considering. And there aren’t a lot of great resources to help them do that.
“It's unique to each community,” Whelton said. “There's been no comprehensive effort to understand how this all fits together, so that utilities can make decisions.”
Although the data is murky, on the whole, there seems to be less concern among experts and advocates with DIP and other metal pipes leaching dangerous chemicals into our drinking water than with PVC and other plastics.
Health concerns for PVC pipes
Given the material’s relatively young age, there are lots of unanswered questions surrounding plastic pipes. Last year, a report from Beyond Plastics, the Plastic Pollution Coalition and Environmental Health Sciences* highlighted research that has identified dozens of toxic chemicals released into water by PVC and chlorinated polyvinyl chloride (CPVC) pipes. It also stressed that there is a lack of data on these chemical leaches into drinking water in “real world” settings.
“We don't have a very good public understanding about the chemicals that are leaching out of a lot of the plastics that we install in our infrastructure,” Whelton said. “PVC pipes are used throughout the United States. And it's a risk that we all face, drinking water from materials that we haven't necessarily tested thoroughly.”
What complicates matters, Whelton said, is a lack of transparency with the testing and safety certification of plastic pipes. Those certifications are handed out by third-party organizations such as NSF.
