Thermoform Fold-and-Form Lining

Advanced PVC-A Lining for Irregular and Large Pipes

Thermoform PVC-A lining represents the next generation of trenchless pipe rehabilitation. This factory-manufactured, fold-and-form solution is ideal for pipes up to 48 inches in diameter, including those with irregular shapes, ovality, or deformation that would challenge traditional CIPP methods.

Technician inserting a PVC liner into a large, old drain pipe

How It Works

A folded PVC-A liner is pulled into the host pipe, then heated with steam or hot water. As the liner heats, it unfolds and expands to fit tightly against the pipe wall, conforming to irregularities and deformations. Once cooled, the liner forms a continuous, structural PVC pipe with a smooth interior surface.

Storm drain lining with PVC fold-and-form technology begins with video camera inspection of the host pipe to identify obstructions. Then the storm drain is cleaned. A winch cable pulls the folded liner through the pipe from the downstream manhole.

 

After stress relief, steam from heat source equipment uniformly raises the liner temperature until it forms to the pipe walls. The liner is then cooled using compressed air or a water-air mixture until exhaust temperatures reach a constant 110°F for at least 20 minutes. This completes the curing process. Finally, robotic cutting machines with CCTV cameras trim the ends and reopen laterals and service connections.

Key Advantages

  • ASTM F1871 compliant — Meets recognized industry standards for thermoplastic pipe liners
  • Accommodates irregular pipes — Conforms to egg-shaped, deformed, or non-circular cross-sections
  • No chemical curing — No styrene emissions, no ambient cure concerns, no resin shelf-life issues
  • Reworkable — Can be cut, tapped, or modified for future lateral connections or changes
  • Long service life — PVC-A offers excellent chemical resistance and structural durability

Ideal Applications

  • Sewer mains with significant deformation or ovality
  • Storm drains with non-circular cross-sections
  • Pipes where CIPP resin curing is problematic
  • Environmentally sensitive areas where styrene emissions are a concern
  • Projects requiring future lateral reinstatement flexibility

Pipe Sizes

TrenchFree install Thermoform PVC-A liners in pipes from 8 inches to 48 inches in diameter, in the South Bay and around the San Francisco Bay Area.