What is a Localised Structural Repair (LSR)

Localised Structural Repair (LSR) is a trenchless method used to restore the structural integrity of a damaged, cracked, or disjointed pipe without the need for full excavation. The process involves the installation of a resin-impregnated patch or short liner directly into the affected section of a drain or sewer, effectively creating a new pipe within the existing one. This technique is widely used in both domestic and commercial drainage systems due to its minimal disruption, cost-effectiveness, and long-lasting results.

LSR is particularly valuable when only a small portion of the pipe is damaged, such as a single crack, joint displacement, or minor root intrusion point. Rather than replacing the entire pipe run, engineers can isolate and repair just the faulty section, reducing labour, time, and environmental impact.

Purpose and advantages of LSR

The main goal of LSR is to restore the watertightness and load-bearing capacity of a compromised pipe, preventing leaks, infiltration, and further deterioration. It is used to:

  • Seal cracks and fractures

  • Bridge displaced or open joints

  • Strengthen weakened pipe sections

  • Prevent root ingress and debris accumulation

  • Extend the life of ageing infrastructure

Some key advantages of Localised Structural Repair include:

  • No need for surface excavation, reducing disruption to roads, gardens, and buildings

  • Rapid installation, often completed in a matter of hours

  • Durable materials with lifespans comparable to new pipework

  • Suitable for use in a variety of pipe materials, including clay, concrete, and PVC

  • Lower cost compared to full-length relining or pipe replacement

Because it targets a specific defect rather than the entire system, LSR is a highly efficient solution for isolated damage.

How the LSR process works

Localised Structural Repair uses a patch liner that is installed using a packer or bladder to press the material against the pipe wall until it cures. The process typically follows these steps:

  1. Inspection and diagnosis
    A CCTV drain survey is conducted to locate the exact position and extent of the defect. The footage helps determine whether LSR is a suitable solution.

  2. Cleaning the pipe
    The damaged section is thoroughly cleaned using high-pressure water jetting or mechanical tools to remove grease, roots, and debris.

  3. Preparing the patch
    A glass-reinforced mat or similar flexible liner is impregnated with a resin (commonly silicate or epoxy) that will harden once cured. The patch is cut to size depending on the length of the defect, typically 0.5 to 1.5 metres.

  4. Insertion into the pipe
    The patch is wrapped around an inflatable packer and pushed or pulled into position within the pipe using access points such as manholes or rodding eyes.

  5. Inflation and curing
    The packer is inflated, pressing the patch tightly against the inner pipe wall. The resin cures within 1 to 2 hours depending on material and ambient temperature.

  6. Removal and inspection
    Once cured, the packer is deflated and withdrawn. A follow-up CCTV inspection confirms that the patch is correctly seated and the pipe is sealed.

The result is a smooth, jointless repair that restores the flow capacity and structure of the pipe with minimal intervention.

Suitable pipe defects for LSR

Not all pipe problems are suitable for localised repair. However, it is ideal for the following defects:

  • Longitudinal or circumferential cracks

  • Open or leaking joints

  • Minor deformities or collapses

  • Root intrusion at a single point

  • Minor infiltration from groundwater

It is not typically used where:

  • The pipe is extensively deformed or collapsed

  • There are multiple faults over a long section

  • The pipe diameter is too small or access is severely restricted

  • There is significant misalignment that would prevent proper seating of the patch

In such cases, full-length lining or excavation may be more appropriate.

Materials and equipment

Localised Structural Repairs use a combination of high-performance materials and specialist tools. The main components include:

  • Resin system: Often silicate-based due to its rapid curing and resistance to moisture

  • Patch liner: Usually a fibreglass or felt mat that bonds tightly with the host pipe

  • Packer: An inflatable device used to position and press the patch against the pipe wall

  • Rods or cables: Used to push or pull the packer into position

  • CCTV equipment: Essential for pre- and post-installation inspection

All materials must be compatible with the pipe’s diameter, condition, and application environment (e.g. temperature, flow type).

Applications in domestic and commercial settings

Localised Structural Repair is widely used across residential, commercial, and public drainage networks. Typical use cases include:

  • Domestic lateral drains with limited access

  • Public sewers under roads or pavements

  • Commercial sites where continuous operation is required

  • Heritage buildings where excavation would be destructive

  • Industrial facilities with chemical-resistant lining needs

In many cases, LSR is used as part of a larger rehabilitation plan, addressing key defects while preserving the wider pipe system until further work is needed.

Regulations and industry standards

In the UK, LSR must be carried out in accordance with Water Industry Specification WIS 4-34-04 and other relevant drainage repair standards. Installers are expected to:

  • Use WRc-approved materials and products

  • Provide documentation of inspections and repairs

  • Ensure the structural repair does not reduce the hydraulic capacity of the pipe

  • Guarantee repairs for an appropriate service life, often up to 50 years

Many professional drainage companies now include LSR as a standard option in their service offerings, especially for reactive repairs or emergency response.

Limitations and considerations

While LSR is effective in many situations, it is not a universal solution. Limitations include:

  • Inability to repair large voids or full collapses

  • Requires clean, accessible pipe conditions

  • Patch liners can slightly reduce internal diameter

  • Not suitable for severe offset joints or pipe dislocation

Good preparation and proper assessment are critical. Misapplied or poorly installed patches can fail to bond, become dislodged, or restrict flow, creating further complications.

Conclusion

Localised Structural Repair offers a reliable, efficient and minimally invasive method for addressing isolated defects in drainage and sewer systems. By inserting a resin-impregnated patch into the damaged area, LSR provides a long-lasting structural solution without the disruption of excavation or full replacement.

It is especially valuable in built-up environments, heritage properties, or situations where time and access are limited. With correct assessment, quality materials and experienced installation, LSR can extend the life of underground assets, restore hydraulic function and help maintain compliance with modern infrastructure standards.