Slip Lining

Summary

    Slip-lining is a trenchless rehabilitation method used to repair or replace existing underground pipelines by inserting a new, smaller-diameter pipe inside the existing deteriorated pipe. This method creates a pipe-within-a-pipe system that restores structural integrity and flow capacity.

    Slip-lining remains one of the most straightforward and cost-effective trenchless rehabilitation methods for underground pipelines when some reduction in diameter is acceptable and the host pipe retains basic structural integrity.

Pre-Installation Preparation

  • Cleaning and inspection of the host pipe.
  • CCTV assessment to identify obstructions or misalignments.
  • Bypass pumping installation (for active sewer/water lines).

    • Installation Steps

  • Excavation of entry and exit pits at terminal points.
  • Assembly of new pipe sections (if not using continuous pipe).
  • Insertion of the new pipe into the existing pipe.
  • Pulling or pushing the liner through the host pipe.
  • Sealing of annular space between pipes.

    • Post-Installation

  • Reconnection of service laterals (requiring small excavations).
  • Grouting the annular space between the new and old pipes.
  • CTesting and commissioning of the rehabilitated pipeline.
  • Restoration of entry/exit pits.

    • Materials Commonly Used

  • High-Density Polyethylene (HDPE)
  • Polyvinyl Chloride (PVC)
  • Fiberglass Reinforced Polymer (FRP)
  • Steel pipe
  • Ductile iron pipe

    • Advantages

  • Minimal surface disruption compared to open-cut replacement.
  • Faster installation than many other rehabilitation methods.
  • No specialized equipment required beyond standard pipe handling.
  • Structurally independent of the host pipe once installed.
  • Long service life of new pipe materials (50+ years).
  • Can navigate through bends (with limitations).
  • Resistant to future root intrusion.

    • Limitations

  • Reduces hydraulic capacity due to smaller diameter.
  • Requires access pits at both ends.
  • Limited to straight or gently curved pipe sections.
  • Service reconnections typically require excavation.
  • Not suitable for severely misaligned or collapsed pipes.
  • Annular space must be properly grouted to prevent voids.

    • Applications

  • Water transmission mains
  • Sewer force mains and gravity sewers
  • Stormwater culverts
  • Industrial pipelines
  • Pressure and non-pressure applications