A recent report from Utah State University Buried Structures Laboratory by Steven Folkman, titled PVC Pipe Longevity Report, used an Australian case study to prove the long-term service of PVC pipes and to assess any deterioration or degradation in their service. Below is an excerpt from the case study used in the report to demonstrate the 100+ year benchmark standard for PVC Pipes.
PVC pressure pipes have been used in Australia for over thirty years. A presentation in 2001 by Stahmer and Whittle1 on the long term performance of these pipes explained that quantifying how long a pipe will remain serviceable is sometimes complicated by misunderstandings surrounding the characteristics of PVC pipes.
The testing methodology used by Stahmer and Whittle takes into consideration the field performance of PVC pressure pipes as well as the actual testing based on the Australian Standards. The pipes which were exhumed in 1996 after 25 years of operation were subjected flattening, resistance, stress, C-Ring and low power magnification tests (click here for more information on these tests).
It was reported that these PVC pressure pipes were installed in a variety of terrains including sandy soil and solid limestone. The performance was reported to have satisfactory in all situations. In addition, these pipes traversed under both roads and rail lines. In neither instance was the pressure class of the pipe upgraded to accommodate the dynamic loads imposed by passing road traffic or trains. Nevertheless, no failures have been reported as a consequence of dynamic load.
The long term performance of the system has been clearly dependent upon the initial pipe quality, handling and installation. Degradation of the PVC material has NOT occurred. For the four pipes tested, both the tensile strength at yield and elongation-at-break were essentially the same. Moreover, the results are the same as expected for contemporary pipes tested at the time of manufacture. Thus is can be concluded there has been no degradation in the strength or elongation characteristics of the PVC during the service life of the pipes. The exhumed pipes have not suffered any loss of strength as a consequence of operating under pressure for almost 30 years.
These results showed there was no deterioration in the fracture toughness during a service life approaching 30 years. A Water Research Foundation study published in 2005 tiled, “Long term performance predictions for PVC pipes,”2 concluded that 100 years is a conservative estimate for a properly designed and installed pipe.
1 Stahmer, M. W., and Whittle, A. J., “long Term Performance of PVC Pressure Pipes in Large Rural Water Supply Scheme,” Plastics Pipes XI Conference, Munich, Germany, Sept 2001
2 Burns, S. et. Al, “Long-term Performance Prediction for PVC Pipes,” AWWARF Report 91092F, May 2006