How our cities got seduced by sewage pipes made of plastic (instead of clay)


Kent Carlson runs the wastewater operations for Los Angeles, which has the largest municipal sewer system in the Northern Hemisphere. “In our city,” he says, “we’ve got clay pipes that are over 100 years old and they’re still operating.”

That history includes two massive earthquakes: the Great Long Beach Earthquake of 1933 (6.4 on the Richter scale, major tremors through 10 Southern California counties, $40 million in damage); and the 1994 Northridge quake (6.7 on the Richter scale, 40,000 buildings damaged in four counties, cost estimated between $13 and $20 billion). Those experiences make Carlson very glad that L.A. never shifted its sewer infrastructure to the plastic pipes that first came on the market in the early 1970s, the way a good many cities have. “We’re building for generations from now,” he says. “That’s not a time to experiment and cross our fingers for 100 years from now.”

That said, cities that do turn to plastic pipes (typically PVC, or sometimes HDPE) do so for some compelling reasons. The question is how good is their reasoning—and the effects on all of us if that reasoning is faulty.


As might be expected, plastic pipes typically cost less than clay—about $5 a foot vs. $8 for clay, says Bryan Vansell of Mission Clay, a longtime manufacturer of clay pipes in Phoenix, Arizona. Many city contractors also find the plastic pipes easier to install. “They never choose clay,” says Brian Schroeder, wastewater collections manager for Kansas City, Missouri. “They’re too heavy, too labor intensive, and their line segments are too short.” Plastic pipes, since they are much lighter, come in much longer lengths, which means a new line can be run much more quickly, with fewer joints that might fail.

Then come questions about the capabilities of today’s laborers. As with so many areas of craftsmanship today, patience and proficiency in the pipe laying industry is in increasingly short supply. With clay pipes, if a laborer isn’t careful, the pipes will crack during installation—often just from setting joints or drilling connection holes. “I’ve got 100 years of people used to being on the backside of a hammer,” says Schroeder. “When a guy is trying to knock out a 4-inch hole, he’ll create cracks that he doesn’t even see.” Those cracks might not leak right away, Schroeder says, but they will over time.

Schroeder admits that his department’s experience with clay is limited, because Kansas City has been using PVC pipes ever since they were first introduced. As Matt Thomas, Schroeder’s man in the field, says, “My experience with clay is fixing it.” Nonetheless, Schroeder admires clay’s virtues. “From a chemical standpoint,” he says, “you cannot beat clay. I love it.”

A “chemical standpoint”? What does this mean? Judging from a variety of reports, that’s the sleeping question.


Like any plastic material, plastic pipes are much more vulnerable to degrading than clay, which essentially never degrades. (As Vansell says, “When they dig up old civilizations, all they find is bones and clay shards.”) And thanks to advances in firing methods since then, today’s clay pipes are much tougher. (They are now “vitrified,” which means treated to such high temperatures in the firing process that the materials within the clay melt, the way sand turns into glass.) This means a city can run almost anything through clay without fear of toxic leaching. Apparently, that is far from the case for plastic.

Plastic pipes are so susceptible to degradation—from chemicals, heat, aggressive cleaning equipment, or pressure—that the municipal infrastructure world has developed a series of terms to describe plastic pipes once they begin to lose their shape.Carlson says “they elongate.” Some call them “egg-shaped.” Jeff Boschert of the National Clay Pipe Institute, a trade organization for clay pipe manufacturers, tries to be a bit more euphemistic. “They develop ovality issues,” he says.

There’s increasing concern that, in the process, the pipes may be releasing toxic chemicals. To date, there have been no confirmed links, but the contents of PVC pipes, and what the manufacturing process produces, has been enough to raise alarm.

Mike Italiano, founder of the U.S. Green Building Council and now Chief Executive Officer of an organization called Market Transformation to Sustainability, has grown increasingly concerned that the pipes may be leaching carcinogens if, or when, they degrade. He points to reports from the National Wildlife Federation and the Environmental Working Group, both of which are particularly concerned about endocrine disrupters from the PVC getting into municipal water supplies.

Even if the pipes don’t leach their chemicals, the process of making PVC generates a substantial amount of dioxin, a proven carcinogen. All of which gives Vansell a handy line to use whenever he’s talking to a potential customer, who is looking at the bottom line, and leaning toward the less expensive plastic pipes. “I always tell engineers, ‘That’s great that you can save some money now. But have you set aside money for replacing these 50 years from now?”

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© 2020 Todd Oppenheimer, all rights reserved. Under exclusive license to Craftsmanship, LLC. Unauthorized copying or republication of this article is prohibited by law.

Published: December 1, 2016