- Material
- Unplasticised PVC (PVC-U)
- Typical system
- Gravity foul and surface-water drainage
- Inspect closely
- Shape, support, joints and branch connections
- Avoid assuming
- That every plastic drain is suitable for lining
PVC-U drainage systems
PVC-U is used in below-ground gravity drainage. The repair decision needs the actual pipe type and dimensions, not colour alone, because plastic systems and product ranges can use different fittings and have different service limits.
The installation around the pipe matters too. Manufacturer guidance covers bedding, backfill and connections. An internal repair does not show that the external support is still satisfactory.
Deformation and joint defects
A leaking joint in a pipe that keeps its shape is different from a flattened or badly distorted section. CCTV should show where the deformation occurs, whether the bore remains reasonably continuous and whether the camera can pass through the affected section.
Standing water can obscure the view. It may suggest a restriction or a problem with levels, but CCTV alone may not show why it is there. The survey record should make the viewing conditions clear.
Lining suitability for PVC-U
The liner system, resin, installation conditions and finished dimensions must suit the host pipe and its use. Internal lining is not a universal answer to distorted plastic pipework and will not correct a defective fall.
Ongoing external movement or inadequate support can reduce the value of an internal repair. Further investigation or local replacement may be needed before the rest of the run is considered for lining.
Survey and completion records
Useful records include pipe identification, survey findings, defect dimensions and the positions of connections that must remain open. A completion inspection should show the repaired section and record its finished condition.