Why We Use Drain Relining

Drain relining — formally called cured-in-place pipe (CIPP) lining — is the most significant technical development in drainage repair in the last three decades. It allows a structurally defective drain pipe to be repaired permanently from the inside, without any digging. For properties in North London where mature trees, Victorian clay drainage, and deep pipe runs create regular structural drain problems, it is often the right solution rather than an option of last resort.

What Drain Relining Actually Does

A conventional drain repair requires excavation: open the ground above the defective pipe, remove the damaged section, lay new pipe, backfill, and reinstate the surface. On a garden path, this is disruptive but manageable. Under a driveway, a patio, or a section of garden with established planting, the disruption is considerably more extensive — and more expensive.

Drain relining repairs the pipe from within, using the damaged pipe itself as a mould for the new one. The process involves:

1. CCTV survey to identify the defect — its location, extent, and the diameter of the affected section. This defines the liner specification.

2. Preparation — high-pressure jetting clears the pipe of debris and root matter. Root cutting removes any established root masses. The pipe interior needs to be clean and free of obstruction before the liner can be introduced.

3. Liner preparation — a flexible felt liner tube, impregnated with a two-part epoxy resin, is measured and cut to the length of the repair section. For a patch repair (a localised crack or joint), the liner is a short section. For a full-length repair (a run of cracked or deformed pipe), it spans the entire affected length.

4. Liner installation — the liner is introduced through the nearest access point — a manhole, rodding eye, or inspection chamber — and positioned at the defective section by an inversion drum or winch system. An inflation bladder inside the liner is then inflated, pressing the liner firmly against the inner surface of the host pipe.

5. Curing — the resin cures against the pipe walls over a period of one to four hours, depending on pipe temperature and the resin formulation. Cold-water cure and ambient-temperature cure are both available; hot-water and UV cure systems are used for larger commercial pipe diameters.

6. Cutting and reinstatement — once cured, any lateral connections (branch pipes joining the main drain) that were covered by the liner are cut open from inside the pipe using a remotely-operated cutter guided by CCTV. The liner ends are trimmed, and a final CCTV inspection confirms the finished repair.

The result is a new pipe within the old one — fully structural, smooth-bore, and seamless from the inside. The liner material has a design life of 50 years or more and is resistant to root penetration.

What Relining Fixes

Drain relining is the permanent solution for the structural defects that cause recurring blockages and leakage in underground drain pipes:

Cracked pipes. Clay pipes crack from ground pressure, frost, and root action. A crack allows ground water to infiltrate (which can cause sinkholes and subsidence) and roots to enter. Jetting clears the pipe; it does not seal the crack. A liner seals the crack permanently.

Displaced or offset joints. Ground movement causes clay pipe joints to shift out of alignment. An offset joint creates a ledge inside the pipe that catches debris and causes recurring blockages. Jetting clears the blockage; the ledge remains. A full-length liner spans the displaced joint and creates a smooth interior, eliminating the ledge.

Root intrusion entry points. Roots enter through cracks and displaced joints. Root cutting removes the root mass; within one or two growing seasons, the roots regrow through the same entry point. A liner seals the entry point and prevents regrowth.

Deformed pipes. Old clay pipes deform under sustained load, becoming oval or partially collapsed. Deformation restricts flow. Where the deformation is moderate, a liner can still be inserted and will restore the bore to the liner’s internal diameter. Severe collapse requires excavation.

Pipe Sizes and Lengths

One of the practical advantages of CIPP relining is its flexibility across pipe sizes. Domestic soil pipes and drain runs are typically 100mm or 110mm in diameter — well within the standard liner range. Larger inspection chamber connections, shared sewer laterals, and commercial drain pipes up to 1.5m in diameter are all linable. For domestic properties in North London, the vast majority of structural drain defects fall in the 100–225mm range where relining is straightforward.

Liner lengths can be short (a 500mm patch repair over a single cracked joint) or long (a 30m or 40m full-run liner from inspection chamber to sewer connection). Where a drain run has multiple defects across its length, it is usually more cost-effective to line the entire run rather than to install multiple short patches, as the mobilisation and material costs are similar.

When Relining Is the Right Choice

Relining is appropriate when:

• A structural defect has been confirmed by CCTV survey
• The pipe can still physically accept a liner (not fully collapsed)
• The defect would otherwise require excavation of a surface that is difficult or expensive to reinstate — a block-paved driveway, a planted garden, a hard-landscaped patio
• The defect is causing recurring blockages that jetting alone cannot prevent

Excavation remains the right choice when a pipe is fully collapsed, when multiple adjacent sections are simultaneously defective at a shallow depth, or when the drain gradient needs to be corrected. In practice, the two approaches are complementary — difficult access sections are lined, straightforward sections are excavated.

London Drain Clear Ltd carries out CCTV surveys and drain relining across Enfield, Barnet, Edgware, Wembley, Cheshunt, Potters Bar and Southgate. If you have a recurring drain problem or a structural defect confirmed by camera, contact us via the enquiry form to discuss whether relining is the right solution for your drain.