Underground sewer pipes can develop cracks, damaged joints, root intrusion and other forms of deterioration over time. Traditionally, repairing significant damage often meant excavating the affected pipe, removing it and installing a replacement. Depending on where the sewer line runs, this could require digging through gardens, driveways, pathways or other areas of the property.
Pipe relining offers another approach for suitable damaged pipes by creating a new structural lining inside the existing pipe. Rather than removing the entire underground line, plumbers can reline sewer pipe sections from within, potentially reducing the amount of excavation required. The process involves several stages, and the condition of the existing pipe must first be assessed to determine whether relining is appropriate.
The Existing Sewer Pipe Is Inspected First
Before relining can begin, the condition and location of the damaged pipe need to be understood. CCTV drain inspection equipment can be passed through the sewer line to provide a view of the pipe interior. This allows technicians to identify issues such as cracks, displaced joints, tree root intrusion and other visible damage while also determining where problem areas are located along the line.
This inspection is important because not every damaged sewer pipe will necessarily be suitable for relining. A pipe that has completely collapsed or experienced significant structural displacement may require a different repair approach. By assessing the line first, the plumber can determine the extent of the damage, measure the section requiring attention and plan the most appropriate method before proceeding with further work.
The Pipe Needs to Be Thoroughly Cleaned
A liner cannot simply be installed over roots, grease, debris or other material inside the sewer. The existing pipe needs to be prepared so that the new lining can form correctly against its internal surface. Depending on the condition of the drain, cleaning may involve high-pressure water jetting and other suitable equipment to remove accumulated material and clear obstructions from the affected section.
Tree roots can require particular attention because they may enter through cracks or deteriorated pipe joints and continue growing within the sewer. Clearing the roots restores access through the pipe, but cleaning alone does not repair the opening that allowed them to enter. Preparing the line for relining therefore serves two purposes: it clears the internal space needed for installation and helps create suitable conditions for the liner to be positioned within the existing pipe.
A Flexible Liner Is Inserted Into the Existing Pipe
Once the sewer has been inspected, cleaned and prepared, a specially designed liner containing resin can be introduced into the damaged section. The liner is flexible during installation, allowing it to travel through the existing pipe without requiring the entire sewer line to be uncovered. Its dimensions and placement need to correspond with the pipe being repaired so that the liner covers the intended damaged area.
The installation method can vary depending on the relining system and the characteristics of the pipe. Once positioned, the liner is expanded so that it sits against the internal wall of the original sewer pipe. This is the key principle behind trenchless pipe relining: the existing pipe remains in the ground and acts as the surrounding structure while the liner forms a new internal pathway for wastewater.
The Resin Cures to Form a New Internal Pipe
After the liner has been positioned correctly, the resin is allowed or encouraged to cure according to the particular system being used. As it hardens, the flexible liner becomes a solid internal structure that follows the route of the existing sewer line. The result is often described as creating a pipe within a pipe because the original line remains in place around the newly formed internal lining.
This new internal surface covers suitable cracks and damaged joints along the relined section, creating a continuous passage through which wastewater can flow. Because the repair is completed internally, extensive excavation may be avoided in suitable situations. This can be particularly useful when sewer pipes run underneath established landscaping, paved areas or other surfaces that would otherwise need to be disturbed to access the pipe directly.
The Completed Liner Needs to Be Checked
Relining does not finish simply because the resin has hardened. The repaired section should be inspected to confirm that the liner has been installed correctly and that the sewer line is ready to return to normal operation. A post-installation CCTV inspection can provide a view of the completed internal surface and help confirm the condition of the relined section.
Any relevant junctions or connections also need to remain functional after the lining process. The exact steps depend on the layout of the sewer and the type of repair being performed. Careful inspection at the end of the work provides a useful record of the completed repair and helps verify that the original damaged section has been addressed as intended before the job is considered complete.
Relining Can Reduce the Need for Excavation
One of the main practical differences between relining and traditional pipe replacement is how the damaged sewer is accessed. Conventional replacement generally requires the old pipe to be physically exposed so that it can be removed and replaced. Relining instead works primarily from within the existing line, which can significantly reduce digging when the pipe’s condition and layout make trenchless repair possible.
Reduced excavation can be particularly valuable when a sewer runs beneath a driveway, garden, pathway or other finished area. However, relining should not automatically be considered suitable for every sewer problem. The type and severity of the damage, pipe material, accessibility and overall condition of the line all need to be considered before deciding whether an internal repair or conventional replacement is the more appropriate option.
Conclusion
Pipe relining works by using the existing sewer pipe as the pathway for installing a new internal liner. The process generally begins with inspection and cleaning before a resin-containing liner is positioned against the inside of the damaged pipe. Once cured, the liner forms a solid new internal surface, and the completed repair can then be inspected to confirm the result.
For suitable sewer damage, this approach can provide a way to repair underground pipework while reducing the need to excavate large areas of a property. The important first step is establishing exactly what has happened inside the sewer, because the condition of the existing line determines whether relining is appropriate or whether another repair method will be required. See more.