Good News On Life Expectancy Of CIPP

A new study just released demonstrating that CIPP appears to have a much longer design life than the 50 years the product touts as a design life. While many claims are made by other technologies that claim to have a better mousetrap than tried and true sewer lining developed in 1970/1971, this study shows that post testing demonstrates that the product is exceeding expectations.

So why the “better than expected” results of materials that have been in the ground for over 40 years? During the development of the ASTM that was drafted for CIPP lining process, many factors were considered regarding the design thickness to withstand years of service in the ground. The design thickness included live load, dead load, ground water, bury depth, original pipe trench width, original backfill materials, type of soil, ovality of host pipe as well as structural physical characteristics  of the tube and resin. After considering all of these factors, conservative engineering dictated a safety factor. The safety factor for this new untested product turned out to be 2 as the engineering community was unsure if the new product would perform as suggested. So while all of the factors used to determine the thickness needed, engineering decided to double the thickness to be safe.

While the first jobs didn’t have an ASTM guide, the first jobs were performed using thicknesses of similar materials to make liner thicknesses such as PVC pipe thicknesses and interpolating the thickness by adjusting for the flexural strength, modulus and tensile strength from known products to the resin/tube set of numbers. Those thicknesses were eventually applied to the CIPP process and the ASTM developed from those early job successes. So we’re at the 46 year mark of the original installation and there have been many 10’s of thousands of miles of the product installed in the ground. And while many competitive processes have tried to tout their processes as a better solution, none have been tested and proven at the levels that the CIPP process has been tested and proven. New processes may prove to be a better fix but until they’ve gone through the application, testing, and the reporting process they remain unproven.

Here’s a chart of the results of real world testing vs. the hypothetical long term estimate of life expectancy. The chart below shows a slope line in orange as the ASTM prescribed deterioration or Creep of the liner over time. The blue slope shows results of the 10,000 hour testing performed years ago on this process, which shows the product actually performing better than the prescribed ASTM model which has the added safety factor of 2 added. The random dots are actual samples tested over time and as we’ve noted in past posts, the material actually increases in strength over time, similar to concrete. Notice that the samples tested at the 30 year mark are actually stronger than the samples taken than the samples taken at 20 years. So you can explain to your customer with confidence that the product will easily last 50+ years and perform as well or better than original sewer piping materials.  Now you know. Here’s the chart: