[University Research] Fall Guy?

Rumors can be devastating to business. During the summer 2001 we heard a rumor that the termiticides we use to protect homes caused chlorinated polyvinyl chloride (CPVC) pipes to bubble and burst when applied at the label rate. Before the year’s end, Florida Pest Control & Chemical Company, headquartered in Gainesville, Fla., brought us a sample of damaged pipes that a builder alleged had been caused by a pretreatment application of Dursban TC (Dow AgroSciences, Indianapolis, Ind.).

THE RESEARCH. The first damaged pipe (see Figure 1 on page 68) seemed to be gashed open, not damage due to a termiticide treatment. We were expecting to see more of the CPVC melted (plasticized) since the only ingredients in Dursban TC at 0.5% (or even 1%) could have been the inert ingredients. We initially disregarded the first pipe’s damage as mechanical and not related to a termiticide treatment — read on if you would like to see how we think even that kind of damage can be caused without gashing the pipe. The parts of the first and second pipe, however, exhibited signs of bubbling, a symptom of some kind of solvent coming into contact with the pipe.

We hypothesized that a solvent caused the bubbling on the pipe. Noveon, makers of probably the most popular CPVC pipes, know that certain chemicals cause the company’s pipes to be compromised. The company even has a Web site dedicated to chemicals that are incompatible with its CPVC pipe (see related story on page 68). But could we demonstrate that termiticides were or were not the culprits in CPVC pipe bubbling?

We set up a laboratory study in order to eliminate any other of the field variables that might be associated with a construction site, such as other "incompatible chemicals." All of our supplies were purchased at Lowe’s Home Improvement store with the goal of testing the most commonly used CPVC pipe (FlowGuard Gold, Noveon), end caps and glue. (We also checked Home Depot for brands of pipe, etc., and found them to be the same.) We even made sure the patent number on the pipes were the same as the sample we received which was implicated in a failure due to Dursban TC.

We immersed a length (about 6 inches) of CPVC pipe in Dursban TC concentrate (see Figure 2 above). By using concentrated Dursban TC, we hoped to accelerate the bubbling process. The label rate for Dursban TC as a pretreatment for termites is between 0.5 and 1%, significantly more dilute than the concentrate. We also poured Dursban TC concentrate into other lengths of CPVC pipe and capped the ends of the pipe to hold the concentrate (see Figure 2 above). Caps were glued in place.

We set up another set of pipe lengths with water used as a control instead of Dursban TC concentrate. After about an hour’s worth of exposure, we checked the tubes and there was no evidence of bubbling or strength loss. We tried snapping the pipe by bending it. We also had several people smell the tubes in which Dursban TC was poured. None of the participants could smell Dursban TC or any solvents permeating through the pipe, further confirming that Dursban TC was not causing any weakness in the pipe material. In the one tube, which was immersed into Dursban TC concentrate, the lettering on the outside of the tube started to disappear, but there was no evidence of bubbling or breakage.

We checked the tubes daily for about a week. (We wouldn’t expect CPVC pipes to be sitting in any termiticide puddle for a week under field conditions, much less in an undiluted form.) The tubes have been sitting in the laboratory with no change in status since mid-January 2002. Testing time is now more than two years and two months of exposure to concentrated Dursban TC and there is still no evidence of bubbling or loss of strength. We are confident that Dursban TC is not the cause of CPVC pipes being compromised.

We want to emphasize that we used the concentrate and not the end-use dilution because if the concentrate did not reproduce the bubbling and breakage, we certainly did not expect the end-use diluted product to produce damage.

ADDITIONAL RESEARCH. Separately, the Florida Department of Agriculture and Consumer Services also was in contact with a private materials testing firm, NSF International. The firm performed a "stress-crack resistance" test on bars using CPVC pipe material. These bars were immersed in undiluted Dursban TC, Demon TC (Syngenta, Greensboro, N.C.) Termidor WG80 or Termidor SC (BASF, Research Triangle Park, N.C.) for 40 hours at 73.4°F and then bent. The final report indicated that the pipes passed their stress tests after being exposed to all the termiticides. In other words, these termiticides did not cause pipe failures in their tests.

The question still remained: "What could cause CPVC pipes to bubble and rupture?" We know that other solvents are present on a building construction site such as glues used to clean pipes and couplers, but could a misapplication of a CPVC glue also cause bubbling and CPVC pipe damage? Our understanding is that the CPVC and PVC glues work by melting (plasticizing) the materials, creating a bond. We checked the Noveon FlowGuard Gold Web site and the company is very specific in its recommendation for "solvent cement application" to CPVC, stating: "Do not allow excess cement to puddle in the fitting and pipe assembly as this may lead to premature failure." We hypothesized that a misapplication of CPVC bonding materials or incompatible glue would seem a more likely avenue to pursue in getting to the bottom of the CPVC pipe failures.

AN ANSWER. We wanted to see what would happen in the event that CPVC bonding material was allowed to sit inside a capped CPVC pipe, against manufacturer directions. The products selected were not on the list of unacceptable products for use with FlowGuard Gold CPVC pipes. We selected products that were designed for use with CPVC pipe: Purple Primer, All Purpose Cement and CPVC Medium Orange (Oatey, Cleveland, Ohio). Materials were painted on CPVC pipe lengths of about 6 inches.
Materials were also poured into capped CPVC pipe lengths to simulate a "puddle" of material. Within 24 hours, the results were dramatic.

Pipes receiving a standard brushed-on application, where the material was not allowed to puddle were in tact. Pipes that received a misapplication (puddle) had softened and begun to collapse (see Figures 3-5 on page XX). What was notable was the splitting and buckling of the CPVC pipe after 24 hours, particularly in the All Purpose Cement application (see Figure 4 on page XX). By 24 hours, all the pipes had completely collapsed and had signs of cracking and splitting. We also could easily bend the pipes filled with Purple Primer, All Purpose Cement and CPVC Medium Orange (see Figure 6 on page XX). This demonstration indicated to us that the "gash" first seen in the pipes brought in by Florida Pest Control & Chemical Company could have been caused by a misapplication of the bonding material. Water pressure or bending could have resulted in the "gash" which hardened after the bonding material evaporated off.

It is interesting to note that the MSDS sheet for all three CVPC bonding products states under its "Materials to Avoid" section that it "(m)ay attack plastic, resins and rubber" because they contain potent plasticizers. The Dursban TC MSDS lists its solvents and states that contact should be avoided with "oxidizing materials and bases," but there is no specific comment addressing plastics, resins and rubber. Noveon does have a section under "chemical compatibility" titled "termiticides and insecticides." While the company discourages "heavy concentrations" of termiticides being applied around CPVC pipes, it states that "light spray applications in an open air-environment, such as slab pretreat applications should not pose a problem."

The authors are an assistant extension scientist and the Margie and Dempsey Sapp Endowed professor, Entomology and Nematology Department, with the University of Florida, Gainesville.