If the damage or erosion is structural but localised or if cracks and service pipes must be closed, “Part-liner” is the ad-hoc system. An expandable cylindrical packer is positioned over the damaged point – previously identified by telecamera. This packer must be longer than the piece to be positioned. Using an expansion procedure the packer applies a pre-impregnated sheath onto the surface of the damaged pipe. The resin penetrates the surface and the piece cements and strengthens it. The part-liner, with a standard length of 50-60 cm, guarantees minimum narrowing of the original cross section and fully restores the static continuity of the pipe and its water-tightness.