ASDSO Dam Safety Toolbox

⚠ Cautions for CIPP in Large Diameter Conduit

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Message: Extra care should be taken to fully expand CIPP liner against large diameter conduit


CIPP was used on this project to rehabilitate an old bituminous coated 48-inch corrugated metal pipe. The downstream portion of the old CMP was replaced with a new reinforced concrete pipe (RCP) and the upstream portion of the old CMP was slip lined with CIPP. The CIPP was installed through an access point at the gate tower and cured with circulating hot water.

After installation and curing was complete, it was noticed that the CIPP did not fit tightly against the existing CMP and there were gaps between the two pipes. Portions of annular space between the CIPP and the old CMP had to be grouted to fill these gaps. The problems with this installation were thought to be caused by the larger size of the original pipe (48-inch) and the distance from the CIPP manufacturing point to the project site. It was speculated that because of the long travel distance to the site, the CIPP began to cure enroute.

  • Judith Basin County, Montana Dam. 55 feet high, 6000 acre-feet. The project rehabilitated an old bituminous coated CMP pipe by replacing the downstream portion with RCP pipe and sliplining the upstream portion with CIPP. Photo: Building upstream cofferdam.

    Judith Basin County, Montana Dam. 55 feet high, 6000 acre-feet. The project rehabilitated an old bituminous coated CMP pipe by replacing the downstream portion with RCP pipe and sliplining the upstream portion with CIPP. Photo: Building upstream cofferdam.

  • Liner arrives on truck. Keeping the liner cool is very important to prevent premature curing.

    Liner arrives on truck. Keeping the liner cool is very important to prevent premature curing.

  • Slip lining upstream portion with CIPP. Access point through gate tower. White pipe – CIPP. Other pipes – hot water to cure pipe in place

    Slip lining upstream portion with CIPP. Access point through gate tower. White pipe – CIPP. Other pipes – hot water to cure pipe in place

  • Upstream end of CIPP line. Hot water is added to promote the curing process.

    Upstream end of CIPP line. Hot water is added to promote the curing process.

  • Note the gap between the liner and conduit.

    Note the gap between the liner and conduit.

  • Liner trimmed to be flush with concrete headwall.

    Liner trimmed to be flush with concrete headwall.

  • The annular space was approximately 1-inch.

    The annular space was approximately 1-inch.

  • CIPP did not cure correctly, not a tight fit, was necessary to go back in and grout portions of annular space between CIPP and old CMP

    CIPP did not cure correctly, not a tight fit, was necessary to go back in and grout portions of annular space between CIPP and old CMP

  • Grout being pumped to fill annular space.

    Grout being pumped to fill annular space.

  • Finished CIPP liner.

    Finished CIPP liner.

  • Liner protruding out of pipe into gate structure.

    Liner protruding out of pipe into gate structure.

  • The liner was trimmed and a stainless steel band was added to provide seal against gate.

    The liner was trimmed and a stainless steel band was added to provide seal against gate.


Note: The content on this page was originally created as part of DamOutletWorks.org (DOWL, 2018). It has subsequently been updated and reformatted as part of the Dam Safety Toolbox.
Revision ID: 3168
Revision Date: 09/15/2022

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