A CIPP felt liner is a flexible polyester or fibreglass felt tube impregnated with resin that is inverted or pulled into a damaged drain and then cured to form a new pipe within the existing pipe. The technique allows structural renewal without excavation and is widely used across London on Victorian clay and pitch fibre drainage. UK installations follow BS EN ISO 11296-4. The liner is cured using hot water, steam or ultraviolet light depending on the resin system, producing a smooth, jointless internal surface that resists root ingress and infiltration. On a post-installation CCTV survey, a CIPP felt liner is identifiable by its uniform pale interior and visible inversion start point at a chamber. The method is generally suitable for runs with consistent diameter and limited deformation.
CIPP felt liner
Resin-impregnated felt tube cured in place to form a new pipe within the existing drain.
