Roots Growing Through CIPP Liner?

Have you ever experienced a root growing through a CIPP liner? I have and while it’s considered a failure, it is a great teaching moment. So how did it happen? My wet out and installation crew was fully seasoned. They’d installed over 1,000,000 feet of CIPP liner, yet here was a root growing through an 8” lined pipe. I got called out because of the root intrusion over our “root proof” liner as we had not joints in the pipe. But there it was, a root growing through the liner, very visible on the CCTV pictures of it and my job was to figure out why and more importantly what I was going to do about it. Closing a city street in Santa Monica was only part of the problem. Other problems were work hours, traffic plates, traffic control during allowed work hours, and finally what kind of fix I would propose.

White spots show lack of resin, therefore allowing roots to grow through the liner.

After getting all the permits needed to open up the street, our first job was to come up with a fix before we started on the remedy. We agreed on a point repair of the liner, but the agency wanted to see why the problem occurred in the first place, hence digging out the failed section of liner and analyzing it. Our bury depth at this location was only 8’, so we used a smaller excavator that got us down to the pipe. We had to include shoring to prevent cave in, and then sent a crew in to cut out a 4’ section of pipe. Once we got it to the surface, the cause was easy to analyze. There was no resin in the area on the tube where the root pushed its way through. These were the days before we added pigment to the resin to more easily identify full saturation. Our resin color was very close to the color of the tube and the guys obviously missed a dry spot in the tube during wet out. As the tube offers not structural strength to the completed composite, the absence of resin in a dry spot would make an easy invitation of roots to grow through.

A couple of lessons from that experience. The first was to make wet out easy to identify wetted out tube from dry tube that’s easily visible. The addition of pigment would take care of that issue. During wet out, it’s much easier to see a dry spot than it is when the tube and resin are close to the same color.

The second lesson was that we needed to regulate the speed of the tube passing through the pinch roller. We had to allow the vacuum pump time to withdraw the entrained air in the liner tube. If we let the liner move through the pinch roller with an air pocket left in the tube, that pocket may never fill in with resin. We needed to insure that we didn’t over run what the vacuum pumps could extract. Nor could we allow the resin slug holding a vacuum break breach the vacuum. In other words let air in past the resin slug by dropping the slug so air could pass through the liner with not vacuum maintained throughout the wet out.

Hopefully this lesson we learned the hard way may keep you from repeating the same mistake. If you are experiencing failures due to root growing through your liners, call us at 888-354-6464 or write to info@pipeliningsupply.com and we will go through refresher training with your installers to prevent this on future jobs.

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