CIPP (Cured-in-Place Pipe) Lining

Why this matters

CIPP (cured-in-place pipe) lining is the trenchless method that lets a contractor rehabilitate a failed sewer line without trenching across the customer's front yard, driveway, or finished landscaping. Done right, CIPP delivers a 50-year service life with one day of work and minimal site disruption. Done wrong, it traps a failed line inside an inadequately cured liner that delaminates in 2 to 5 years, and the customer ends up paying for both the failed CIPP and the full trench replacement that should have been done in the first place. The technical work is repeatable; the project-selection decision (which lines are CIPP candidates and which are not) is where most failed CIPP projects start.

What CIPP actually is

A felt or fiberglass tube ("the liner") impregnated with a thermosetting resin (epoxy, polyester, or vinyl ester) is inverted or pulled into the host pipe. The liner is pressed against the host-pipe wall by air, water, or steam pressure. The resin cures (heat, UV, or ambient temperature), forming a structurally-independent new pipe inside the old one.

Once cured, the new "pipe in pipe" is structurally sound on its own and bonded to the host. Outside-pipe failures (further root intrusion, future cracks) do not affect the liner; the liner is the new flow path.

ASTM F1216 governs the standard for CIPP rehabilitation. ASTM F2019 covers pulled-in-place lining; ASTM F2599 covers UV-cured lining.

Where CIPP works

Best candidates:

• Continuous run with no major branches in the section to be lined (or branches that can be reinstated by robotic cutting)
• Pipe diameter in the residential and small-commercial range (4 inch through 12 inch typical; up to 60 inch for municipal)
• Host pipe with structural integrity remaining (the liner conforms to the host shape; a fully collapsed host cannot be lined)
• Length under 200 ft for residential, longer for municipal
• Material is cast iron, clay, concrete, or even PVC (any rigid material with structural shape)
• Access to one end (one-sided pull or invert; two-sided improves quality but is not required)

Poor candidates:

• Completely collapsed host (the liner has nothing to conform against)
• Severely deformed host (ovaling over 30 percent; liner takes the wrong shape)
• Heavy infiltration (groundwater entering during cure produces a poor bond and weak liner)
• Multiple severe offsets at joints (the liner cannot bridge step changes in shape)
• Active wet conditions that prevent dewatering before cure
• Galvanized steel host with heavy scale (liner does not adhere well to scale)

Curing methods

Three curing methods cover most residential and commercial CIPP work:

Steam cure

Steam at 180 to 220 F pressurizes the liner and activates the resin. Cure time 2 to 6 hours depending on diameter and resin chemistry.

• Pros: fast cure, widely available, well-understood
• Cons: requires steam boiler and water source; more equipment on site

Hot water cure

Heated water at 140 to 180 F pressurizes the liner. Cure time 4 to 8 hours.

• Pros: gentler than steam, lower energy
• Cons: slower; requires large water source

UV cure (light cure)

Resin formulated to cure under UV light. After the liner is inverted, a UV light train is pulled through the liner, curing in 30 to 90 minutes per typical length.

• Pros: fastest cure, smallest crew, no thermal equipment
• Cons: requires fiberglass liners (felt does not transmit UV); higher equipment cost; quality-control via in-process temperature monitoring

UV cure has been gaining residential share since 2018; most modern shops are buying UV equipment for new install or replacing aging steam rigs.

Ambient cure

Some resin systems cure at ambient temperature over 24 to 72 hours. Used for emergency situations where heat or UV equipment is unavailable, or for specific resin formulations.

Resin systems

Residential sewer lines almost always use polyester or vinyl ester. Potable-water service lines (yes, you can line potable lines too) require epoxy and NSF/ANSI 61 certified product (3M Scotchkote 169LV, Nu Flow, Pipe Restoration).

Step-by-step CIPP procedure

Step 1: Pre-line inspection

Run a sewer camera (see sewer camera image interpretation reference) to document:

• Material, diameter, condition
• Length to be lined
• Branch locations (these must be reinstated after lining)
• Existing cleanout and access points
• Any deformations or structural issues that affect cure

Document with video; this is the baseline for the warranty.

Step 2: Cleaning

A CIPP cannot bond to grease, scale, debris, or soft material. Pre-cleaning is mandatory:

• Mechanical descaling (chain knocker, descaling tool) for cast iron with heavy scale
• Hydrojetting at 4,000 to 8,000 psi for grease and soft debris
• Root cutting for any remaining roots
• Final inspection camera pass to verify cleanliness

A line that is not properly cleaned produces a CIPP that delaminates within 1 to 3 years. This step is the single highest-leverage quality control in the entire procedure.

Step 3: Bypass and dewater

The line cannot have flowing water during inversion and cure. Bypass:

• Block the line upstream
• Pump flow around the lining section
• Drain residual water from low spots
• For residential, schedule with the homeowner to minimize flow (no laundry, dishwasher, showers during the lining window)

Step 4: Liner preparation (wet-out)

The dry felt or fiberglass liner is impregnated with resin in a controlled "wet-out" process:

• Resin mixed at exact specification (resin plus catalyst, weighed and timed)
• Liner pulled through a wet-out machine that distributes resin throughout the fabric
• Saturated liner sealed in a refrigerated transport cooler if not immediately deployed (resin pot life is short at ambient)

Wet-out is typically done on the truck or at the shop. Off-site wet-out requires keeping the saturated liner cold (under 50 F) until install.

Step 5: Inversion or pull-in

Two installation methods:

References

• ASTM F1216 (Standard Practice for Rehabilitation of Existing Pipelines and Conduits by the Inversion and Curing of a Resin-Impregnated Tube).
• ASTM F2019 (Pulled-in-Place CIPP).
• ASTM F2599 (UV-cured CIPP).
• NASSCO LACP (Lateral Assessment Certification Program).
• NSF/ANSI 61 (for potable-water-side lining).
• EPA Effluent Limitation Guidelines.
• Manufacturer literature: Insituform, Perma-Liner, LightStream UV, MaxLiner, AquaBlast LiteRoad UV.
• Manuall internal: Plumbing Sewer Camera Image Interpretation, Plumbing Trenchless Sewer Repair, Plumbing Clear Main Sewer Line.