Some material costs can be saved by using a thinner liner on a pipe rehab job. But how do you figure out when it’s worth taking that route?

Recently, I received this question:

“I took your advice and read the ASTM F-1216 that pertains to CIPP inversion lining. I noticed that there is a lot of detail about determining thickness of liner based on whether or not the line is fully deteriorated or only partially deteriorated. I’m confused on when a pipe is ‘partially deteriorated’ and when it’s ‘fully deteriorated.’ Can you clarify the difference? Can I line pipe that is only partially deteriorated with a thinner liner and save some costs for tube and resin by going thinner?”

I commend this person for reading the ASTM. There is a lot of good information in that document, as well as the documents that accompany it, but that’s another blog post.

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When I was learning plumbing practices, I was taught that the difference between a broken pipe that’s considered partially deteriorated versus one that’s fully deteriorated is the condition of the breaks in the pipe. A pipe with a circumferential break in the pipe is considered partially deteriorated. In other words, the pipe will support the loading around it — both dead load and live loads — with the exception of the direct area that is broken.

On the other hand, a longitudinal break indicates that the pipe is fully deteriorated. A crack or break that travels in the alignment of the pipe section means the pipe can no longer support the loading factors and is in fact beginning to fail. A clay pipe with a crack in the length or a cast iron pipe with the bottom eroded away indicates the pipe’s life is over or close to over.

Here’s where a decision needs to be made. The decision has to take into account how long the partially deteriorated pipe’s life will be if a partially deteriorated lining solution is applied. Most likely not the 50 years that you could achieve if you applied a fully deteriorated design to the fix. The few dollars saved on the installation process usually doesn’t justify this approach on a 30- or 40-year-old existing pipe.

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Now if the pipe you are trying to rehab has only been in the ground a couple of years and a defect was found that didn’t threaten the structural integrity of the pipe, a thinner liner would be appropriate. If you have the host pipe in a fully deteriorated mode, you don’t have a choice on which method to pick. A fully deteriorated pipe that demands a full structural liner will give the owner the peace of mind that he’s getting solution with a 50-year design life if the old host pipe disappears.

With the little amount of money saved going with a thinner liner, most customers would rather start a rehab job with the equivalent of new pipe as opposed to a Band-Aid fix that will extend the life of an old line a few years.

About the author
John Heisler is the owner of Pipe Lining Supply and Quik-Lining Systems Inc. He has 20 years of experience in the CIPP lining industry and over 40 years in the underground construction industry.

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