On June 11, The Plastics Pipe Institute (PPI) issued what it called a "cautionary advisory" (read a copy here) regarding the integrity of fusible polyvinyl chloride (PVC) pipe. PPI said that fusible PVC pipe is susceptible to rapid crack propagation (RCP) and that this characteristic has led to a number of recent water pipeline failures. In particular, the group cited a failure in Naples, Fla., in May 2008, in which a newly installed 36-inch fused PVC water main cracked, causing significant damage and requiring costly repairs.

Underground Solutions, Inc. (UGSI), supplier of the fusible PVC pipe used in Naples, immediately responded with a letter to customers (click here to read) defending fusible PVC pipe performance and detailing what it called "misleading claims" and "inaccuracies" in PPI’s press release.

According to PPI, RCP has various causes, including defects in the pipe and damage incurred during production and shipping, as well as the base resin and thin wall of fusible PVC pipe used in trenchless applications. "Recent failures of new water lines using this novel fusible PVC material and its fusion method have exposed a critical problem to the media and to the industry," said Tony Radoszewski, executive director, PPI. "Fusing together lengths of high-density polyethylene (HDPE) pipe is a time-proven method, and the PPI has spent decades researching and evaluating fusion techniques of HDPE to earn the confidence of the underground utility industry. However, this long history of proven performance does not necessarily translate to new materials. Employing fusion techniques developed for HDPE to other materials, without extensive, industry-wide testing is risky."

"This is simply not true," responded UGSI in its letter. "Fusible PVC pipe has not experienced a single in-service failure due to RCP. PPI goes to great length to create a false comparison between HDPE and PVC with respect to RCP, going so far as to state that RCP has ’plagued’ Fusible PVC pipe installations. Yet the only Fusible PVC pipeline failure mentioned by PPI, in Naples, Fla., did not involve RCP. … The Naples pipeline experienced a joint separation—there was no cracking at all. Out of the hundreds of projects we have successfully installed, we have had two pressure test failures that involved cracking due to compressed air generating enormous stored energy—as they would for any other pipe system."

PPI also raised concern about compliance of installed fusible PVC pipe with industry standards from groups such as the American Water Works Association (AWWA). "I’m concerned of reports indicating the AWWA standards are now appearing on the fusible PVC print string because the thermal joining or butt-fusing of PVC pipe is not covered by AWWA C900, C905, and C605," Radoszewski said.

In addition, PPI noted that operating conditions for making a fused joint are more constraining for fusible PVC pipe than for HDPE pipe. "The melting temperature and curing temperature require much more precision with the fusion machine when used for fusible PVC," Radoszewski said. "PVC fusion is more sensitive to heat exposure time than HDPE, and there is very little latitude. … This may not be practical in the field, especially on large PVC pipe diameters."

UGSI responded that based on installation of more than 1 million feet of PVC using its butt fusion method, the joint failure rate is approximately 0.05 percent (about one failure per 80,000 feet). "All fusion technicians, whether employed by us or working for one of our licensed contractors, are required to use data-loggers to provide joint quality and traceability," the company told customers. "On the other hand, there are a lack of meaningful standards for HDPE fusion in the water industry (AWWA C906 and M55 both simply refer to each individual manufacturer’s recommendations, which vary among the manufacturers). In other words, the HDPE industry has almost no idea if their fusion operators are qualified, the conditions of the fusion, or the ultimate failure rate in the field."

Look for the claims and counterclaims to continue. PPI scheduled a free webinar on July 17 (registration required) to "explore these and other issues relating to fusible PVC and discuss the long-term benefits of HDPE pipe."

For its part, the PVC pipe industry, represented by the Uni-Bell PVC Pipe Association, called the press release a propaganda campaign by PPI. "Cautionary advisories coming from a competing industry and about a competing product are inherently suspicious, or at least they should be viewed with great skepticism," said Bob Walker, P.E., executive director and Atlantic region engineer for Uni-Bell. "Uni-Bell was, quite frankly, both surprised and disappointed that PPI and their members would resort to such a negative-sell campaign."