A new study published by Utah State University buried structures laboratory has taken a comprehensive review of the longevity of PVC pipes in service in a range of countries – including Australia. The conclusion?
The combination of pipe examination and testing date in conjunction with previous pipe break studies and dig-up reports of pipes in service support PVC's longevity and performance in excess of 100 years.
We think that even 100 years could be considered a conservative view as we really don’t know how long in-service PVC pipe is going to last. There is nothing in nature that attacks or degrades PVC pipes and it doesn’t suffer from oxidation or corrosion like alternative pipe materials.
Study author, Steven Folkman in an interview with Plastics Today said, “Understanding the longevity of pipes improves the ability of a water utility to make better infrastructure investment decisions with improved affordability results for customers”
Folkman knows that the report will be met with skepiticim from the Ductile Iron industry whose ductile iron pipes are failing due to corrosion.
“Saying how long pipe will last is a little debatable,” Folkman said in a telephone interview. “Talk to a ductile iron guy and he’ll say: ‘They haven’t proven anything.’ The point of my paper is that it just isn’t me.
“Here’s about 20 other different sources and they are all saying about the same thing. We pulled the information together, including some that we gathered. We’re saying here is a mountain of evidence and all of our honest indications are if the PVC pipes are properly produced and properly installed, all the data indicates the longevity is in excess of 100 years,” Folkman told Plastics News.
A major finding of the study is that water utilities can reduce water main breaks and operations and maintenance costs by including corrosion-proof PVC piping in their replacement programs. Earlier research by USU showed that corrosion of iron piping is a major problem for water systems and newer metallic pipes are experiencing failures more rapidly than older types because of their thinner walls.
The report did acknowledge that there were some early PVC pipe failures, however both Australian and international tests on failed pipes older than 20 years showed the failures were due to low gelation levels of the PVC when the pipe was first products. Significant advances in material, processing and testing technologies over the past two decades have virtually eliminated this problem.
The comprehensive nature of this study has proven several national recommendations and rules of thumb which utilities can use for benchmarking and procurement purposes.
- Dig-up test results indicate the PVC pipe can be expected to provide reliable service in excess of 100 years
- The average water main is failing at 47 years. Corrosion is the major cause
- Utilities using non-corrodible pipe materials are able to reduce the number of water main breaks
- Many utilities still have the ability to reduce water main breaks and reduce operating and maintenance costs by utilising non-corrodible pipes on their replacement and procurement strategies
- Internationally, PVC dig-up reports support the previous findings of PVC having the lowest water main break-rate
- Improving installation and inspection practices have been shown to contribute to lower failure rates and increased pipe longevity and affordability
- Dig-up studies on PVC pipe materials around the world report no degradation after decades of operational service
- Recently excavated PVC pipes, some nearly 50 years old were tested and met applicable standards. They are expected to easily exceed 100 years of service life.
- PVC pipes offer a high degree of resilience in freezing conditions and after 25 years meet virtually all new pipe requirements
- PVC pressure pipes exhumed after being in operation for almost 30 years have not suffered any loss of strength. All tested pipes would be expected to exceed 100 year life under normal operating conditions.
- After over 35 years of operation, PVC pipes have virtually no change in mechanical properties due to ageing. Both ductility and resistance to internal pressure are still on the same level as new pipes
- Based on stress regression, slow crack growth and fatigue test, the service life of PVC pressure pipe should exceed 100 years
- The water Research Foundation reported that 100 years is a conservative estimate for properly designed and installed PVC pipe
- Life cycle costing provides a basis to financially evaluate pipe selection over a 100 year period
- Including the realistic costs of corrosion control mitigation  for ductile iron pipes over the 100 year period for all pipe sizes is critical in developing a comparable evaluation of PVC pipe costs and ductile iron costs.
 Corrosion mitigation methods approved by the National Association of Corrosion Engineers