The long service life of plastic pressure pipe systems is increasingly recognised across the pipe sector. Industry bodies commonly refer to an expected service lifetime of more than 100 years and are now discussing how 100-year design life could be reflected in standards using the Categorized Required Strength (CRS) concept developed within the ISO pressure rating system.
For PVC-U pressure pipes, VinylPlus Pipes has gone one step further by funding dedicated research into the relationship between extrusion conditions, gelation degree and long-term hydrostatic strength as predicted by the ISO 9080 statistical extrapolation method.
This research, which started under PVC4Pipes and was carried out by CEISLAB (formerly CEIS), supports the technical evidence base for designing PVC-U pressure pipe systems for a 100+ year design lifetime under optimised processing and quality-control conditions.
Classification Maintained for 100+ Years
The final CEISLAB test report confirms that the tested PVC-U pressure pipes maintained PVC-U Class 250 classification at both 50 and 100 years.
Based on the ISO 9080 extrapolation method, the tested pipes reached minimum statistically expected values of hoop stress extrapolated over 50 years and 100 years of, respectively, σLPL,20°C,50y = 26.465 MPa and σLPL,20°C,100y = 25.749 MPa. In other words, the pipes remained above the 25 MPa threshold required for PVC-U Class 250, after 100 years.
| Temperature | Time | σLPL | Classification |
|---|---|---|---|
| 20°C | 50 years | 26.465 MPa | PVC-U Class 250 |
| 20°C | 100 years | 25.749 MPa | PVC-U Class 250 |
Processing Conditions: Why Quality Control Matters
The research also shows that a 100+ year design lifetime is linked to optimised processing conditions
The extrusion temperature, DSC B-onset temperature and gelation degree all influence the long-term hydrostatic strength of the pipes.
The findings support the use of Differential Scanning Analysis (DSC) analysis for quality control governed by the ISO 11357 standards
Together, the results show that 100+ year design lifetime cannot be simply a generic material claim. It depends on appropriate processing and quality-control conditions.
In the research, achieving the required 100-year Lower Prediction Limit was linked to optimal extrusion temperature, DSC B-onset temperature and gelation degree, while excessive processing delivered only marginal gains and increased the risk of degradation.
What This Means for Utilities and Network Owners
For utilities, network owners, designers and specifiers, the research provides a stronger technical basis for considering PVC-U pressure pipes in long-term water infrastructure planning. The results indicate that, under appropriate processing and quality-control conditions, PVC-U pressure pipes can support a 100+ year design lifetime using the same design basis normally applied to 50-year pipe designs.
This can help inform material selection, tender documentation, asset-management planning and lifecycle assessments where durability, long-term reliability and reduced replacement needs are important decision factors.
Documentation
CEISLAB. (2026). Classification according to UNE-EN ISO 12192:2009 of PVC-U pipes manufactured by Adequa Water Systems S.L. based upon UNE-EN ISO 9080:2013 long-term hydrostatic strength analysis [Test report]. CEISLAB.
Final test report confirming that the tested PVC-U pressure pipes maintain PVC-U Class 250 classification at both 50 and 100 years.