A Closer Look at the Pipe Lining Process

Sewer pipe lining may appear straightforward once the job is finished: a damaged sewer line becomes a smooth, seamless pipe without the extensive excavation required for traditional replacement.

What happens behind the scenes is in fact extremely precise.

Also known as cured-in-place pipe (CIPP) lining, the process requires careful inspection, cleaning, measurement, resin preparation, liner saturation, installation, and curing. Each step helps ensure the new liner fits the existing sewer line correctly and forms a durable new pipe within the old one.

Bob Oates crew during a sewer pipe lining procedure, ready to reline the homeowner’s below ground sewer pipe

Here’s a closer look at how the process works and what Bob Oates technicians are doing at each stage.

Start With a Sewer Camera Inspection and Pipe Preparation

The process begins with a sewer camera inspection to evaluate the existing pipe, locate damage, identify connections, and determine whether the line is a good candidate for CIPP lining.

Not every damaged sewer should be lined. A severely collapsed pipe or other structural conditions may require a different repair method, making the initial inspection essential for choosing the appropriate solution.

A Bob Oates technician monitors a live sewer camera feed while inspecting underground drain lines.

If lining is suitable, technicians thoroughly clean the pipe. The techs at Bob Oates use high-pressure water jetting (also called hydro jetting) to remove roots, scale, buildup, and other material. This prepares the host pipe so the liner can conform closely to its interior and create a smooth finished surface.

Prepare and Saturate the Pipe Liner

The new pipe begins as a flexible textile liner manufactured for CIPP installation.

Our technicians determine the required liner length and calculate the amount of resin needed based on the dimensions of the sewer line. The resin components are then measured and mixed according to the requirements of the installation.

Air is removed from the dry liner with a vacuum system before the prepared resin is introduced. The liner then passes through a roller-based impregnation table. The rollers apply controlled pressure while the vacuum helps distribute the resin throughout the liner material.

Bob Oates technicians install sewer liner as part of a combined pipe repair and full sewer lining project in Ballard.

This process, known as resin impregnation or “wet-out,” helps ensure the liner is thoroughly and consistently saturated before installation.

By the time this stage is complete, the flexible liner has been measured, prepared, and impregnated with the resin that will form the new sewer pipe once cured.

Install the Liner Through the Inversion Process

One method of installing a CIPP liner is known as inversion.

After the liner is prepared, technicians load it onto specialized equipment called an inversion drum. One end of the liner is positioned and secured at the drum outlet, and the system is pressurized.

Rather than simply pushing the entire liner through the sewer, air pressure progressively turns — or inverts — the flexible liner inside out as it travels through the existing pipe.

Think of turning a sock inside out, except the process is controlled by specialized equipment and takes place through an underground sewer line.

Bob Oates crew completes a trenchless CIPP lining and cleanout installation as part of a sewer repair project.

As the liner inverts, its resin-saturated surface is positioned against the interior of the existing pipe. Controlled pressure keeps the liner expanded so that it conforms to the shape of the host pipe, including damaged areas, cracks and joints along the run.

This allows technicians to rehabilitate a long section of underground sewer from limited access points rather than excavating the entire line.

Cure the Liner to Create the New Pipe

Once the liner is correctly positioned, it must be cured while held tightly against the existing sewer pipe.

Depending on the lining system and project, curing may use different technologies. Bob Oates crews use modern curing equipment, including UV/blue-light technology, to harden compatible liners efficiently and precisely.

On this trenchless sewer repair job, Bob Oates techs installed 70 feet of 4-inch liner using blue light curing — restoring service in hours with no digging required. Traditional methods can take up to 48 hours and involve major excavation.

As the resin cures, the flexible liner becomes a rigid, durable pipe inside the original sewer line.

After curing is complete, the installation is inspected and the sewer is returned to service. The finished CIPP liner provides a smooth, seamless interior without the joints found in many older sewer systems.

The result is not simply a coating over the damaged pipe. It is a new structural liner installed and cured within the existing sewer line, with a projected lifespan of up to 50 years.

Comparison Table: Pipe Lining vs. Traditional Excavation

When the existing sewer line is a good candidate, professional CIPP lining can provide several advantages:

The right repair depends on the condition and configuration of the sewer line. A professional camera inspection provides the information needed to determine whether pipe lining, another trenchless method, or conventional sewer repair is the best approach.

See the Pipe Lining Process in Action

For homeowners, one of the biggest advantages of understanding the lining process is knowing exactly what you are purchasing.

Much of the work happens underground, but the installation itself involves specialized equipment, experienced technicians and a carefully controlled sequence from inspection through curing.

Give Bob Oates a Call!

Bob Oates Plumbing, Sewer & Rooter provides trenchless sewer pipe lining throughout Seattle and all surrounding communities. Our team can inspect your sewer line, explain what the camera reveals and determine whether CIPP lining is an appropriate long-term repair for your property.

If you’re experiencing recurring sewer problems or have already been told that your sewer line needs repair, just call the office or contact Bob Oates online to schedule an inspection and learn more about your options — our estimates are always free, and that includes getting a second opinion.

Frequently Asked Questions About the Pipe Lining Process

What is CIPP pipe lining?

CIPP stands for cured-in-place pipe. It is a trenchless repair method that installs a resin-saturated liner inside an existing sewer pipe. The liner is positioned against the old pipe and cured until it forms a rigid new pipe within the existing line.

How is the liner installed inside a sewer pipe?

CIPP liners can be installed using specialized methods including inversion. During inversion, controlled air pressure turns the liner inside out as it travels through the existing sewer line, positioning the resin-saturated surface against the host pipe.

Why does a sewer line need to be cleaned before lining?

Roots, scale, debris and other buildup can interfere with proper liner installation. Cleaning the sewer line—often with hydro jetting—prepares the interior so the liner can conform properly to the existing pipe.

How does a pipe liner harden?

Once the liner has been installed and positioned, the resin is cured to transform the flexible liner into a rigid pipe. Depending on the lining system, curing technologies may include UV or blue light, heat or other manufacturer-specified methods.

Can every damaged sewer line be repaired with pipe lining?

No. Pipe lining is appropriate only when the existing sewer line meets the requirements for a successful installation. A sewer camera inspection helps determine the extent of the damage and whether lining, pipe bursting, excavation or another repair method is the better solution.

How long does sewer pipe lining last?

Properly installed CIPP liners are designed as long-term sewer rehabilitation solutions and can provide decades of service. The expected lifespan depends on the lining system, installation conditions and application.