- Material
- Vitrified clay
- Typical system
- Underground gravity drainage
- Inspect closely
- Joints, fractures, alignment and connections
- First evidence
- CCTV survey with defect location and dimensions
Vitrified clay drainage systems
Vitrified clay is widely used for underground drainage. The pipe barrel and its joints need separate attention: sound clay pipe does not mean every joint is still watertight or correctly aligned.
Clay performs well with many chemicals, but that does not make every installation suitable for an industrial discharge. The effluent, joint seals, fittings and any proposed liner all need to be compatible. For a particular system, use the relevant manufacturer guidance.
Clay pipe defects on CCTV
A local crack, a displaced joint, root entry and major movement are different faults and can need different repairs. Cleaning may be needed before the pipe wall can be inspected properly, but cleaning does not repair a broken pipe.
The survey should locate the defect, record the internal diameter and show branch positions. Footage is more useful when each finding is tied to a measured distance and the route of the drain.
Lining suitability for clay drains
Lining may provide an internal repair where the host pipe and route are suitable for the selected system. Severe displacement, collapse, a restricted bore or an unsuitable connection can instead require local excavation or another repair method.
A liner follows the existing route; it should not be assumed to correct a poor fall. The repair specification should say what the liner is intended to seal or strengthen and what will remain unchanged.
Repair records and completion checks
The completion record should show the repaired length, product or method used, how branch connections were dealt with and the final inspection. The original CCTV survey should remain with that record so the condition before and after the work can be compared.