Pipe Lining
Trenchless pipe lining solutions rehabilitate, protect and renew ageing pipeline infrastructure, restoring performance and extending asset life with minimal excavation.
Radius Subterra delivers controlled, efficient installations that reduce disruption and support long-term asset reliability across gas, water and industrial networks.
Trenchless pipe lining solutions are used to rehabilitate, protect and renew ageing pipelines, with minimal excavation and disruption. Radius Subterra delivers controlled, efficient lining installations that restore performance and extend asset life across gas, water and industrial networks.
Radius Subterra provides a range of trenchless pipe lining technologies designed to renew existing pressure pipelines without full excavation or open-cut replacement These methods install a new internal lining within the host pipe, reducing installation time, limiting the size and number of excavations, and enabling continued use of existing pipeline routes.
Our close-fit polyethylene (PE) lining systems include RollDown™, and Subline™.
- Rolldown™ uses a thick-walled PE liner that is diameter-reduced, inserted, and then reverted under pressure to form a tight-fitting internal pipe.
- Subline™ uses a folded thin-walled liner inserted via slip-lining and reverted to a circular profile to create an interactive close-fit lining.
These systems are suitable for rehabilitating steel, ductile iron, cast iron, and asbestos cement pipelines. Depending on design requirements, they can function as fully structural, semi-structural, or interactive lining solutions, forming a continuous polyethylene pipeline within the host main.
In addition to close-fit PE lining, Radius Subterra delivers Subcote™ spray lining, a centrifugally applied resin coating used to protect and stabilise ageing metallic pipelines. This smooth, solvent-free lining improves hydraulic performance while addressing corrosion, tuberculation, and water quality concerns in potable water networks.
Radius Subterra provides an end-to-end pipelining service including asset assessment, cleaning, liner supply, fusion welding, insertion, spray application, and final commissioning. By selecting the most suitable lining method for each asset, we deliver rehabilitation in a safe, controlled and efficient manner aligned with industry practices and asset-owner requirements.
Key Benefits
Minimal excavation required
Close-fit and spray lining methods significantly reduce excavation requirements, enabling long pipeline sections to be rehabilitated with minimal ground disturbance, reduced reinstatement requirements and less operational disruption.
Extended asset life
Installing a new internal liner creates a renewed pipeline within the host main, allowing ageing assets to remain in service and supporting long-term operational reliability without full replacement.
Flexible technology selection
Multiple lining systems suit varying diameters, materials and conditions, ensuring the most appropriate rehabilitation method is selected for each asset, network requirement and operational constraint.
Pipe Lining technologies
Trenchless pipe lining technologies delivering close-fit polyethylene (PE) and spray-applied lining solutions that renew, protect and rehabilitate pressure pipelines across gas, water, and industrial networks.
Rolldown™
Rolldown™ is a close-fit polyethylene (PE) lining system developed by Radius Subterra for the rehabilitating existing pressure pipelines. The system uses pressure-rated PE pipe materials typically ranging from SDR 33 to SDR 11 (SDR is diameter‑dependent), which are concentrically reduced in diameter using a controlled roller process. This allows the liner to be inserted into the host main before being reverted to form a tight‑fitting internal pipe.
Rolldown™ is suitable for water, wastewater, gas, sewer and industrial pipeline applications where full replacement is impractical or disruptive. The system is available for pipe diameters from 100 mm to 500 mm, using standard approved PE materials. Radius Subterra provides a complete service including liner supply, fusion welding, diameter reduction, and installation.
Before insertion, the liner is butt-fusion welded into installation lengths and the diameter is roller-reduced by approximately 10% to allow controlled insertion while maintaining fusion joint integrity. Once positioned, the liner is pressurised with cold water to revert towards its original diameter, forming a close-fit internal PE pipeline with minimal loss of hydraulic capacity.
The reverted liner forms a continuous, close-fit, pressure-rated polyethylene pipe that can operate as a fully structural or semi-structural solution, depending on project requirements. The resulting liner performs independently of the host pipe’s structural condition, providing long‑term performance and corrosion resistance.
Rolldown™ is commonly used to rehabilitate steel, ductile iron, cast iron, asbestos cement and PVC pipelines, providing a trenchless renewal method that limits excavation and reduces disruption. Radius Subterra delivers the full process, including liner preparation, fusion welding, diameter reduction, insertion, reversion and reinstatement, to ensure controlled, compliant and efficient rehabilitation.
Subline™
Subline™ is a site-folded close-fit polyethylene (PE) lining system, developed by Radius Subterra in partnership with GPS (now part of Aliaxis). It is used to rehabilitate pressure pipelines where access is limited and retention of hydraulic capacity is essential. A thin-walled PE liner is butt-fusion welded into long continuous lengths, folded into a compact profile, and secured for insertion using conventional slip-lining techniques.
This technique is widely used to renovate ageing pipelines, particularly where the host pipe remains largely structurally sound but requires internal protection, sealing, or life extension. Typical applications include potable water and raw water mains, sewer pumping (force) mains, oilfield water injection lines, and industrial water pipelines. Subline™ is suitable for a wide range of host materials including steel, ductile iron, cast iron and asbestos cement.
During installation, the liner is passed through specialist forming equipment that folds it into a reduced cross‑sectional profile, creating clearance for long‑distance insertion within the host pipe. Once positioned, the liner is pressurised with cold water, causing the retaining restraints to release and the liner to revert back to a circular profile. This creates a close‑fit lining against the internal wall of the host pipe. End terminations and connections are then completed using standard, approved PE fittings.
Subline™ is available for pipe diameters from 75 mm to 1600 mm, with thin‑wall PE liners selected to suit the host pipe and operational requirements. The folded configuration allows the liner to negotiate gradual bends and enables long insertion lengths, often exceeding 1,000 m in a single pull. Installation requires only small entry and exit excavations, reducing surface disruption and reinstatement costs.
As a thin-walled system, Subline™ generally functions as an interactive or semi-structural liner, forming a continuous, corrosion‑resistant PE lining within the existing pipeline. The smooth bore and close‑fit characteristics help maximise retained flow capacity while sealing joints, bridging small gaps, and mitigating further internal deterioration.
Radius Subterra delivers the full service, including liner supply, welding, folding, insertion, reversion, and final commissioning to ensure controlled, efficient rehabilitation.
Subcote™ spray lining
Subcote™ is a spray-applied resin lining system developed by Radius Subterra for the internal protection and rehabilitation of metallic pipelines. Applied using a centrifugal spray process, the resin forms a smooth, continuous coating on the internal pipe wall, improving water quality and protecting against further internal deterioration.
This technology is widely used across potable water networks where ageing metallic mains suffer from corrosion, discolouration, or sediment build-up. The solvent-free polyurethane formulation is approved for use in contact with drinking water and can be applied both in new manufacture and in-situ to existing assets requiring renovation.
The resin is pumped through specialist equipment, mixed immediately before application and atomised through a rotating spray head to ensure an even coating along the internal pipe surface. Lining thickness typically ranges from approximately 1 mm to 5 mm in a single pass, with greater thicknesses achievable where required through specialist application expertise and controlled installation techniques, depending on host pipe condition and required protection level.
Subcote™ is suitable for cast iron, ductile iron, steel and cement-mortar lined pipes across diameters from around 75 mm to 1500 mm. The system is primarily used to address internal corrosion and water quality issues rather than provide full structural renewal.
Fast-setting resin technology allows pipelines to be returned to service quickly following application, with Subcote™ lining enabling same-day return to service for water supply in many applications – a key advantage where customer disruption and shutdown durations must be minimised. Radius Subterra delivers the complete service, including pipeline preparation, cleaning, spray application, curing, and commissioning, using approved materials and specialist application equipment.
Our other solutions
Explore other Radius Subterra solutions designed to enhance safety, efficiency and long‑term performance.
Under Pressure Connections
Pre-Insulated Pipework
Pressure Testing
Pipework Installation & Mainlaying
Pipe Cutting
Manufacture & Fabrication
Engineering and Project Management
Pipeline Repair & Maintenance
Flowstopping
Our other solutions
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Under Pressure Connections
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Pipeline Repair & Maintenance
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Under Pressure Connections
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Pipeline Installation & Mainlaying
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Pre-Insulated pipework
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Pressure Testing
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Pipe Cutting
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Manufacturing/ Fabrication
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Engineering & Project Management
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Pipe Lining
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Case Studies
Discover the prowess of Radius Subterra through our latest case studies.
Witness how we excel in tackling intricate pipeline challenges with innovative solutions and state-of-the-art technology. Stay tuned for more videos showcasing our commitment to engineering excellence.
Faced with severe leaks in a critical 1500mm trunk main, Radius Subterra provided an innovative pipeline rehabilitation solution using their close-fit PE liner system. This approach restored the pipeline’s integrity
Discover how Radius Subterra’s precision engineering revitalises a historic London waterway with cutting-edge pipeline solutions, installing a bespoke branch saddle onto a live water main in Finsbury Park. This job
Radius Subterra partnered with Anglian Water to solve leak issues in a hard-to-reach 10” water pipeline in East Anglia. Using their innovative Rolldown & Slipline method, Subterra maximised pipe bore
In February an accidental incident occurred that resulted in a 10” gas main being damaged, and a hole being drilled into the main. The incident was near to the main
Case Studies
Discover how Radius Subterra delivers safe, innovative and technically assured solutions across the UK’s most challenging pipeline environments.
Faced with severe leaks in a critical 1500mm trunk main, Radius Subterra provided an innovative pipeline rehabilitation solution using their close-fit PE liner system. This approach restored the pipeline’s integrity
Discover how Radius Subterra’s precision engineering revitalises a historic London waterway with cutting-edge pipeline solutions, installing a bespoke branch saddle onto a live water main in Finsbury Park. This job
Radius Subterra partnered with Anglian Water to solve leak issues in a hard-to-reach 10” water pipeline in East Anglia. Using their innovative Rolldown & Slipline method, Subterra maximised pipe bore
What our client’s say about us
Why choose Radius Subterra?
Trusted expertise, engineered solutions and a service approach shaped around your challenges.
For decades we’ve supported utility networks in the UK and beyond with safe, reliable and efficient pipeline services. Our teams combine technical knowledge, industry-leading equipment and a problem-solving mindset to deliver high-quality outcomes with minimal disruption. Whether planned works or complex operational challenges, we provide proven capability and dependable support.
Decades of expertise
With deep roots across the wider Radius Group and extensive experience in live gas, water, biogas and pipeline rehabilitation operations, our teams bring exceptional hands-on knowledge to every project. We understand the pressures faced by network operators and contractors and deliver work that is safe, compliant and technically robust from start to finish.
Committed to quality and safety
Safety underpins every service we deliver. Our work follows industry standards, rigorous internal procedures and environmental best practice. From accredited techniques to specialist equipment, we ensure consistent quality while reducing risk, waste and unnecessary disruption across gas, water and biogas networks.
Minimising disruption
Our specialist techniques, including under-pressure connections, flowstopping and trenchless rehabilitation, allow essential works to continue while maintaining customer service, protecting highways and minimising community impact. Reduced excavation and streamlined operations, support faster reinstatement and lower overall disruption.
Innovation and customisation
From bespoke branch saddles to tailored fittings for non-standard assets, innovation is central to our approach. We engineer solutions to suit each site, material and operating condition, enabling safer, faster and more cost-effective outcomes across complex project environments.
Safety and sustainability
We champion safe working and long-term sustainability. Our methods reduce carbon, excavation material, traffic disruption and reinstatement, while modern equipment and ongoing training create a safer environment for teams and the public. Every project is designed and delivered with environmental responsibility and operational resilience in mind.
Decades of expertise
With deep roots across the wider Radius Group and extensive experience in live gas, water, biogas and pipeline rehabilitation operations, our teams bring exceptional hands-on knowledge to every project. We understand the pressures faced by network operators and contractors and deliver work that is safe, compliant and technically robust from start to finish.
Committed to quality and safety
Safety underpins every service we deliver. Our work follows industry standards, rigorous internal procedures and environmental best practice. From accredited techniques to specialist equipment, we ensure consistent quality while reducing risk, waste and unnecessary disruption across gas, water and biogas networks.
Minimising disruption
Our specialist techniques, including under-pressure connections, flowstopping and trenchless rehabilitation, allow essential works to continue while maintaining customer service, protecting highways and minimising community impact. Reduced excavation and streamlined operations, support faster reinstatement and lower overall disruption.
Innovation and customisation
From bespoke branch saddles to tailored fittings for non-standard assets, innovation is central to our approach. We engineer solutions to suit each site, material and operating condition, enabling safer, faster and more cost-effective outcomes across complex project environments.
Safety and sustainability
We champion safe working and long-term sustainability. Our methods reduce carbon, excavation material, traffic disruption and reinstatement, while modern equipment and ongoing training create a safer environment for teams and the public. Every project is designed and delivered with environmental responsibility and operational resilience in mind.
Contact us
Ready to progress your next pipeline project?
Radius Subterra’s specialist engineering teams are here to support you with safe, efficient and technically assured solutions across every stage of the asset lifecycle.
Get in touch by phone or email to discuss your requirements and speak directly with our experts.
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