It’s over 40 years since the basic Cure In Place Pipe (CIPP) technique was invented by Eric Wood, an agricultural engineer, when he repaired a pipe in a mushroom farm. His next repair was a sewer under Hackney, a district of London, England. The industry which he invented single handed is now one which has simplified the maintenance of pipes and sewers worldwide. It is one of several methods known as ‘trenchless repairs’, although the technique is used above ground as well as below.
The original CIPP concept was a felt sheet soaked in resin which was pulled into place inside a pipe. Wrapped in plastic, it was airtight and then inflated in place. The resin then cured. The so-called inversion method uses water or air pressure to unroll a tubular liner in the pipe or sewer.
Pipes from 3” diameter upwards can be lined, with 96” being the largest successful sewer installation. Continuous repair runs of up to 1,500 feet in length are routinely achieved.
Materials and Techniques
Felt is still common as a liner material. Both woven and non woven polyester felts are used, with an outside coating of polyurethane. CIPP is effective in pipes with bends, though careful design and installation is required to prevent wrinkling on the inside radius; excessive stretching on the outside radius may cause porosity.
The techniques vary depending on the resin system used - curing of the resin/liner matrix may be by ambient air, hot water, UV light or steam. One installation approach using thermosetting resin involves wet-out of the liner at the manufacturer’s plant. Then, the liner is transported in a refrigerated truck to the installation site, with water driving the inversion and then steam being used to initiate curing. Cooling rates are controlled to avoid shrinkage.
Depending on particular circumstances, some installers may inject additional epoxy resin into defect areas with voids. Lateral junctions have to be reinstituted which can be done using remote drilling systems or even manually in larger liners.
Market and Industry
Eric Wood’s original company, Insituform, patented the process and was dominant for 23 years. The business grew successfully in the US and internationally using a franchise model. In the US, much sewer and water pipe repair work is commissioned by the public sector and the need for competitive bidding for work was an issue when Insituform had no competitors. However, the cost savings and disruption saved by not have to dig up a city center (e.g. Madison Avenue in New York) were such that they could not be ignored and Insituform continued to grow.
When Insituform’s patents expired, there was a huge growth in competition and also strong pressure to innovate further to reduce costs and retain market leadership. Other companies innovated too, and the market in the US is now thought to worth over a billion dollars a year.
Advantages of CIPP
The finished pipe-within-a-pipe is a jointless repair which can be installed without any trenching (except in the largest of installations). Because the finished interior is smooth, detritus build up in sewer pipes is minimized and flow rates are improved even though there is a small reduction in diameter due to the liner.
The repaired pipe, sewer or drain is much more resilient to small ground movements then the legacy structure, and tests on 30 year old installations have indicated great durability and almost no degradation. The use of CCTV systems has enabled much more localized (and economic) repairs to be carried out.
The Future of CIPP
It is a growing market as older pipes, sewers and storm drains installed in the 19th and early 20th centuries are increasingly failing. Growth will stabilize and perhaps even stall at some point, when all brick sewers, concrete drains, and cast iron pipes have all been repaired. However, that is likely to quite a long way down the pipeline.