People hear “epoxy” and picture the two-part kit from the hardware store. Part A, Part B, stir it together, pour it on the garage floor, wait a day.
That is a coating. A cured in place pipe liner is a structural pipe. They share a chemistry family and almost nothing else, and the difference explains why lining went from a genuine gamble to one of the most predictable repairs in the trade.
A coating sits on a surface. A liner carries a load.
Floor epoxy has one job: stick to concrete and resist wear. Nobody expects it to hold up a driveway.
A CIPP liner is engineered as a load-bearing pipe. Under ASTM F1216, the cured liner has to meet specified minimums for flexural strength and flexural modulus, because on a badly deteriorated line the liner is not helping the old pipe. It is replacing it structurally. The soil above it, the groundwater around it, the truck driving over it, all of that load goes into the liner.
The liner we install is a fiberglass scrim. The epoxy is poured into the tube and then pressed through the material by machine, so the resin saturates the fiberglass completely before anything goes in the ground. Once it cures, the fiberglass and the epoxy are one solid pipe, seamless from the house to the city main.
You buy it as fabric. It comes out a pipe.
This is the part that trips people up, and it is worth slowing down on.
A liner arrives as a roll of fiberglass cloth. It feels like heavy fabric because that is what it is. We buy it in lengths of roughly 380 to 390 feet and cut what the job needs, so a 60 foot run leaves a short offcut behind.
The epoxy gets poured into the tube, and the tube runs through a machine that presses the resin all the way through the material. That step matters. The resin has to reach every fiber, because a dry spot in a liner is a weak spot in a pipe.
Then it goes into your sewer still soft, and the light cures it.
What comes out is not a coating on the wall of your old pipe. It is a pipe. The fiberglass and the epoxy harden into a single solid wall, thinner than a stick of Schedule 40 PVC but close to it, and it runs seamless from your foundation all the way to the city main. No joints, no couplings, nothing glued.
The best way to understand it is to hold a cured piece. We keep one on the truck, cut out of a pipe we lined and then broke open on purpose. People pick it up expecting something flexible and find they are holding pipe. You can hit it with a hammer.
That distinction has a practical consequence. Roots get into old sewer pipe at the joints, because a joint is a gap and roots are very good at finding gaps. A liner has no joints. If a root cannot grow through PVC, it is not growing through this either. It has to find another way around, and there is no way around.
What the old method got wrong
Cured in place pipe was invented in 1971 by Eric Wood, an agricultural engineer in London. He impregnated a felt tube with polyester resin, dragged it 230 feet into a brick sewer, and inflated it with air.
It worked, and it set the standard for the next several decades: a two-part epoxy, an A side and a B side mixed together exactly like a garage floor kit, cured by pumping steam or hot water into the line and waiting.
Done perfectly, that is a good pipe. The problem is how many ways it can go wrong.
Too hot and it cures before it expands. On a hot day the resin can begin setting while the liner is still being placed. If it hardens before it has fully pressed against the pipe wall, you have a liner that is not doing its job.
Too cold and the job takes over a day. In cold conditions that line may need steam or hot water held in it for 24 hours or more. During all of that time the homeowner cannot use the sewer. Not the toilets, not the shower, not the washing machine.
Styrene. Two-part systems off-gas during cure, the same way spray foam does when the A and B sides react. The compound is styrene, and people who are sensitive to it can have real problems around it. There are also long term health questions attached to styrene exposure that the industry has been working away from.
None of those are hypotheticals. They are the reason lining had a reputation problem for years.
What light curing changed
Instead of mixing two parts and applying heat, a light-cured system uses a liner pre-impregnated with a resin that sets when a specific wavelength of light reaches it. A light head is drawn back through the pipe and cures the resin as it travels.
If you have had a filling at the dentist, you have seen the same principle. The material goes in soft, the light comes in, and it hardens on command.
What that removes:
- No waiting for heat to do its work. The cure happens as the light passes, not over hours of holding temperature.
- No 24 hour sewer outage. Most residential jobs are done in a single day.
- No styrene off-gassing from a two-part reaction.
- No guessing whether it cured. The light head carries a camera and the pull-back speed is calculated for the job.
That last one matters more than it sounds. On our system the pull-back rate is set from the pipe diameter, the temperature, and the condition of the light head itself, down to whether a single bulb has burned out. The controller accounts for it and adjusts. A steam cure has no equivalent. You hold temperature for the recommended time and you hope.
The part nobody talks about in a Duluth winter
Here is the consequence that matters most in this climate.
A steam or hot water cure depends on ambient heat. In deep winter, in frozen ground, that becomes difficult enough that some lining contractors in this region simply stop lining for the winter. January through March, the service is not available from them. Ours is, and our CIPP lining service page covers what that involves.
A light cure does not depend on ambient temperature the same way. The light provides the energy. We line year round.
If your sewer backs up in February, that is not an academic distinction.
One warning: not all epoxy in a pipe is a liner
There are contractors who spray an epoxy coating on the inside of a pipe and market it as “pipe lining.”
Spray-applied coating has legitimate uses. It is not structural CIPP. A coating a few millimeters thick bonded to a failing pipe is not a load-bearing pipe, and it will not carry soil load if the host pipe gives up.
How to tell them apart:
- A structural liner is installed as a tube and cured in place. A coating is sprayed or brushed on.
- A structural liner is designed to a standard (ASTM F1216 for inversion, ASTM F1743 for pulled in place) with a calculated thickness. A coating has a mil thickness.
- A structural liner is built for a 50 year service life as a pipe. A coating is a surface treatment.
If a quote says “epoxy lining” and comes in far below everyone else, ask which of the two you are buying.
What to ask before you sign
- How do you cure it? Steam, hot water, or light.
- If it is steam or hot water, how long will my sewer be out of service? Get the honest number, including on a cold day.
- Do you line in the winter? If the answer is no, that tells you what the cure method is.
- Is this a structural liner or a coating? There is no wrong answer, only a wrong assumption.
- What standard are you installing to? ASTM F1216 or F1743.
What we run
We use Hammerhead equipment and Hammerhead lining materials throughout, with the Bluelight LED curing system, which cures with visible blue light at 444 to 457 nanometres rather than ultraviolet. Hammerhead builds it in Wisconsin, outside Madison, which means when we need a part or service we drive a few hours rather than waiting on a shipment from overseas.
Before any liner goes in, the pipe is cleaned with a Picote high-speed cleaner. Chains first to cut out root intrusion, then a sanding head to take the pipe wall back to clean material. A liner bonded to roots and buildup is a liner that fails, so this step is not optional and it is where a lot of the job really happens.
For most residential work we use a flex liner rather than a standard scrim. A standard liner inflates to one fixed diameter. A flex liner follows the shape of the pipe it is in, which matters here because the common setup in this area is 4 inch cast iron leaving the house that transitions to 6 inch clay partway out. The flex liner handles that transition in one continuous piece.
We back our lining work with a 10 year warranty. The liner itself is tested to a 50 year service life.
See it for yourself
Every job starts with a camera inspection, and we include it free on service calls. You watch the screen with us and see the same footage we do before anyone talks about resin, thickness, or price.
Contact us or call 218-409-6356.