Pipe lining is a method of repairing damaged underground pipes from the inside, without digging them up. A flexible tube soaked in resin is inserted into the existing pipe, then hardened in place to form a smooth, new pipe wall inside the old one. The technique is part of a broader category called trenchless repair, and it’s used on everything from residential sewer lines to large municipal water mains. Most projects can be completed in a single day.
How the Process Works
The most common form of pipe lining is called cured-in-place pipe, or CIPP. The process follows a consistent sequence regardless of whether you’re dealing with a backyard sewer lateral or a city stormwater line.
First, a crew clears the pipe of tree roots, debris, and buildup using high-pressure water jets and specialized cutting tools. They run a camera through the line to inspect the damage and confirm that lining is a good fit. If wastewater needs to keep flowing during the work, a bypass system reroutes it to nearby pipes. A vacuum truck keeps the pipe dry and clean throughout.
Next, the liner itself (a flexible felt or fiberglass tube saturated with resin) is fed into the pipe through an existing access point like a manhole or cleanout. It’s pushed or inverted into position using air or water pressure so it presses tightly against the interior walls of the old pipe. Once in place, the liner is exposed to heat (steam or hot water) or ultraviolet light, which causes the resin to harden. This curing process transforms the soft tube into a rigid, jointless pipe within the old one.
After curing, the crew reopens any side connections that the liner covered, such as lateral sewer lines feeding into a main. The bypass system comes down, and a final camera inspection confirms the liner is properly seated and smooth. From start to finish, the active work typically takes about 24 hours, with post-repair finishing adding at most another half day.
Resins and Materials
The resin that saturates the liner is what gives the finished product its structural strength. Two main types dominate the industry: epoxy and polyester.
Epoxy resin is a two-part system that offers strong adhesion to the host pipe, excellent waterproofing, and high resistance to chemicals and temperature swings, including freeze-thaw cycles. It’s the preferred choice for structural repairs and lines exposed to harsh conditions. It also produces lower levels of volatile organic compounds during curing, making it the greener option.
Polyester resin costs less and cures faster, which makes it attractive for simpler, non-structural jobs. The tradeoff is weaker adhesion (with a higher chance of the liner separating from the pipe wall over time), more brittleness under sustained pressure, and less tolerance for temperature changes. Polyester-based installations also release more chemical fumes during curing and require better ventilation.
The liner fabric itself is typically polyester felt or fiberglass, chosen based on the pipe diameter, the severity of damage, and whether the repair needs to be fully structural (meaning the liner alone can support the load) or simply seal leaks and smooth the interior.
Where Pipe Lining Is Used
Sewer lines are the most common application, both for residential laterals running from a house to the street and for larger municipal mains. Pipe lining works well on materials like cast iron, clay, PVC, and concrete, which covers the vast majority of underground drainage systems.
It’s also used on stormwater pipes, industrial process lines, and in some cases, drinking water lines. Water supply applications use epoxy brush coating or specialty liners rated for contact with potable water, since the materials must meet stricter safety standards than those used in waste lines. Sewer applications have more flexibility in material choice because the water inside isn’t consumed.
Cost of Pipe Lining
For a typical residential sewer line, pipe lining costs between $1,900 and $6,000 per project, with a national average around $2,900. On a per-foot basis, lining runs $135 to $150 per linear foot, assuming the existing pipe isn’t severely collapsed or misaligned.
If the old pipe needs to be broken apart first using a technique called pipe bursting, costs climb to $150 to $190 per linear foot. Longer runs raise the total significantly. A 75- to 100-foot sewer line replacement can range from $4,500 to $25,000, depending on depth, access, and local labor rates.
These numbers generally compare favorably to traditional excavation, which carries additional costs for digging, shoring, backfilling, repaving driveways or streets, and restoring landscaping. Those restoration expenses alone can sometimes rival the cost of the pipe work itself.
Pipe Lining vs. Traditional Excavation
The biggest advantage of lining over dig-and-replace is speed and disruption. A trenchless lining job on a residential sewer can often be done in a single day. Traditional excavation for the same line can take several days to weeks once you factor in digging, pipe replacement, backfilling, and surface restoration. Permitting, weather delays, and traffic management for street-level work can stretch that timeline further.
Trenchless lining needs only minimal access points, typically one or two openings rather than a trench running the full length of the pipe. That means no torn-up yards, no broken driveways, and no blocked streets. It also means less labor, fewer heavy equipment hours, and no post-project landscaping bills.
Traditional excavation still has its place. Pipes that have fully collapsed, lost their shape, or shifted so badly that a liner can’t follow the original path often require physical replacement. But for pipes with cracks, joint separation, root intrusion, or moderate corrosion, lining handles the job with far less collateral damage.
How Long a Lined Pipe Lasts
Municipalities typically design CIPP installations for a 50-year service life, and real-world evidence suggests that’s a conservative estimate. An EPA-funded study that examined CIPP liners with up to 34 years of service across nine North American cities found little evidence of deterioration. The liners’ strength and stiffness measurements showed no meaningful decline over time.
The study concluded that properly designed and installed CIPP liners should meet and likely exceed 50 years, with some test results supporting expected lifespans of 100 years or more. Other rehabilitation technologies in the study, including PVC fold-and-form liners and high-density polyethylene liners, also exceeded their required performance benchmarks after 14 to 19 years of service.
The key qualifier is “properly installed.” Liner longevity depends on correct resin saturation, full curing, and good contact with the host pipe. Shortcuts during any of those steps can lead to early failure.
When Pipe Lining Won’t Work
Lining isn’t a universal fix. Pipes that have fully collapsed or lost their round shape can’t support a liner because there’s no stable interior surface to bond to. Severe misalignment at joints, where one section of pipe has shifted significantly relative to the next, can also make lining impractical.
Incompatible pipe materials or unusual pipe geometries (sharp bends, for instance) can complicate installation. If a pre-lining camera inspection reveals conditions that make a full lining risky, a contractor may recommend a partial approach: replacing the severely damaged section with new pipe and lining only the viable portions. For isolated problem spots, patch repairs that cover just a few feet of pipe are another option.
Chemical Emissions During Curing
One concern worth knowing about is chemical off-gassing during installation. The curing process releases volatile organic compounds, primarily styrene when polyester-based resins are used. A multi-site study published in the International Journal of Environmental Research and Public Health found that styrene concentrations directly above the work area during curing exceeded occupational safety thresholds at some sites, reaching levels above limits set by NIOSH.
For the general public, the risk appears low. Styrene concentrations dropped substantially just five feet downwind from the work site and were undetectable at twenty feet. The primary concern is for the installation crew, who need proper respiratory protection and air monitoring. For nearby residents, the main precaution is keeping windows and doors closed during the curing phase, since vapors can occasionally migrate into buildings through small openings. Epoxy-based resins produce lower emissions than polyester, which is one reason the industry has been shifting toward them for urban installations.