Pre-Liner – When Should I Use It?

Pre-Liner

“I’ve read your blogs and you refer to pre-liner often. I’m still unclear when to use it and what to use. Can you clarify this issue? Thanks!”

Many of you still are worried that unless the liner you install sticks to the wall of the host pipe, you won’t have a good liner. If you were trying to rehabilitate a partially deteriorated pipe, this assumption may be true as you are filling in non-structural defects in pipe with material that removes those defects with your repair. In earlier posts we’ve discussed partially deteriorated pipe vs. fully deteriorated pipe, and if you are unclear, please refer to that archive at and find that topic Structural vs. Non Structural Lining Rehabilitation. In the event you are not using that type of design bear in mind the materials most suppliers provide you assumes that the pipe you are fixing is fully deteriorated. With that in mind, we don’t care about sticking any resin to the host pipe, nor do we care what the future holds for the original host pipe. All we’re looking for is a form to use to cast our new liner into that will form a new fully structural “stand alone” pipe if no host pipe or section of host pipe is present. If we approach our repair this way, a pre-liner is our form that we’re using to cast our liner.

With those issues defined, let’s look at when to use a pre-liner. The most often applied use for pre-liner is to prevent water that may be infiltrating into the host pipe from washing away our resin before it is cured. Ever noted water coming in after you’ve swabbed it out? This is infiltration and is depending on how much is coming in as well as how fast and under what pressure, the water may wash away the resin. Typically, the installer would install a pre-liner from the installation end most all of the way to end of the liner to insure you disperse any water away from the resin. So if ground water is present or suspected if not evident, use a pre-liner.

The second most use of a pre-liner is for pipe that has missing sections. Most often the missing section of pipe is the bottom of cast iron that’s been eaten away. By installing a pre-liner, you will insure that the new liner will retain a round shape as pipe is suppose to be instead of a semi round pipe with a u in the bottom of it. Sometimes portions of cracked up clay pipe are missing or all of the pipe is gone with an excavators bucket removing it, a pre-liner is in order to be used as a form.

Another application of pre-liner is to insure that the pipe can be lined. Have you ever found a test wye put in backwards to the flow for testing a lateral during construction that was left there? When a liner comes up to the wye, it doesn’t know which way to go, and may stop. Any time you are not sure whether your liner will negotiate the pipe to be lined, a pre-liner shot in advance will tell you whether the liner will go or not. If the pre-liner went through, leave it there and line through it. It’s a good bet the liner will follow the pre-liner successfully.

Finally a pre-liner may help with containing resin from running up a tie-in. When you see 2″ to 3″ of resin cured in a tie-in that you have to chew out to reinstate the lateral, you’ll be happy you pre-lined it.

One other benefit of a pre-liner is cost. You can salvage old used calibration tubes to be used as pre-liners. Salvage them from current jobs, measure what you salvaged, roll them up, and mark the length on the outside of the roll. When you need that length for a job, you have it in your hands and your cost is $.00.

So there you go, you can use a pre-liner when you need to and it won’t hurt your job even if the liner isn’t sticking to the wall of the host pipe.

 

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