Correcting falsehoods about PVC is why we built Vinyl Verified.  And the Ductile Iron Pipe Research Association (DIPRA) just validated the need for this platform.

A recent DIPRA blog post irresponsibly deceives readers about PVC. In it, DIPRA not only blatantly disregards the facts about our material, but also conceals a core failure of iron pipe noted in the very article the group props up to promote its dishonest arguments.

The article DIPRA references quotes a Marshfield, MA public official stating that salt water may have “rotted out” the bottom of a local iron pipe that had split.  But that reference is conveniently missing from DIPRA’s blog post, which makes a number of unfounded assertions regarding PVC’s ability to withstand colder temperatures.

Let’s review the facts:

PVC pipes are not disproportionately vulnerable to cold weather. It’s why PVC pipes are extensively used in Canada and northern U.S. cities. Calgary and Edmonton switched to PVC piping for its durability in cold weather and reduced costs. And cities in the U.S., from Alaska to Colorado to Maine, have also successfully made the switch to PVC.

PVC pipes have the lowest break rates. Studies show PVC pipes have the lowest break rates compared to other pipe materials. PVC had only 2.6 breaks per year for every 100 miles of pipe. Iron piping fared much worse - with ductile iron having 4.9 breaks and cast iron with 24.4 breaks.  A study by the National Research Council (NRC) of Canada reports that the average break rate per 100 miles of pipe for ductile iron is 15.87, compared to PVC at only 1.17 breaks over the same distance. And the NRC report shows that ductile iron pipe breaks 13.57 times more than PVC pipe – a differential that has a significant impact on overall repair costs.

PVC piping has a design life of 100 years or more. PVC pipe not only has a 100-year + life span, but municipalities using PVC pipes have experienced savings in the order of 30 to 70 percent compared to ductile iron piping. Since PVC is corrosion-proof and does not degrade over time, operations and maintenance costs are much lower than for iron pipes which have to be replaced and repaired frequently. Corroding metallic pipes are the major cause of water leaks in underground piping networks. While PVC is non-corrosive and the thickness of the pipe wall does not impact corrosion, metallic pipes - such as cast iron - are vulnerable to environmental conditions. Ductile iron pipe fares far worse, having a wall thickness of only one-fifth that of cast iron.*

PVC can perform in any soil condition. When installation guidelines are properly followed, PVC piping has a 100-year lifespan, regardless of the conditions. But DIPRA doesn’t want readers to know that the most common type of ductile iron pipes have a life expectancy of only 11 to 14 years in moderately corrosive soils. That’s why the city of Indianapolis, IN found that PVC water piping was 2.5 times more successful than tradition materials that corrode and increase costs.

More municipalities are switching to PVC pipe. The City of Burton, MI, is replacing its dilapidated iron pipe with PVC pipes, and the Mayor was recently recognized with the 2015 Innovation in Infrastructure and Technology award from the Genesee County Metropolitan Planning Commission for leading this initiative. Using PVC instead of ductile iron pipe will save taxpayers almost $2.2 million when all five phases of Burton’s 19-mile iron pipe replacement project are completed.

PVC Pipe Doesn’t Leach Toxins Into the Water Supply. PVC pipe has been verified by NSF International and is designed to minimize environmental impacts due to its corrosion resistance. PVC pipe and fittings are resistant to chemicals generally found in water and sewer systems, preventing any leaching or releases to ground and surface water during the use of the piping system.

Ductile Iron Pipe Is Thinner Today, Contributing to Its “Shorter Useful Life”:  According to a National Taxpayers Union (NTU) study, “ … the thinner wall of ductile iron pipe is one of the factors that contribute to its shorter useful life compared to cast iron. Historically, the extra thickness of the cast iron pipe provided more metal for corrosion to attack (i.e., a corrosion allowance). As shown in the chart below, the historical wall thickness difference in some cases can be as much as 75 percent thinner for a similar pressure and diameter pipe. If the wall thickness of ductile iron is only one-fifth of the cast iron wall thickness and the corrosion rate is the same, then the expected life of ductile iron will be substantially less than for cast iron in similar corrosive environments. The difference in wall thickness is one consideration that must be taken into account during corrosion evaluations and selection of control methods. Some utilities are specifying increased ductile iron pressure classes for additional wall thickness in an attempt to provide a larger corrosion allowance.”  

The walls of ductile iron pipe are made thinner than cast iron, a 76 percent reduction in wall thickness since 1908. ... The simple fact is that thinner metallic pipes, under similar soil and moisture conditions, corrode and fail more quickly than their thicker cast iron predecessors.
— U.S. Conference Of Mayors
Nearly 75 percent of all utilities have corrosive soil conditions and combined with a high portion of old cast iron and ductile iron pipes, corrosion is ranked the second-highest reason for water main pipe failure in the United States. When comparing older cast iron and newer ductile iron, thinner-walled ductile iron is experiencing failures more rapidly.
— Steven Folkman, Utah State University

*Courtesy of National Taxpayers Union  


PVC Is Cost Efficient: Pleasanton, CA Mayor, Jennifer Hosterman, noted that use of ductile iron pipe for repairs and infrastructure expansion “greatly increased initial material and placement costs.” Since 2001, more than 90 percent of Pleasanton’s pipe installations have included “corrosion-proof” PVC, which, according to the city’s construction manager, is “about 70 percent cheaper than ductile iron.” Today, PVC represents nearly one third of the city’s water and wastewater lines.  

We understand DIPRA has a financial motivation to protect its own interests. But that doesn’t give it the right to misinform the public by mischaracterizing PVC. It’s important to know the facts about PVC, and we will continue to use this forum, Vinyl Verified, to advance them moving forward.