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BS EN ISO 11297 — Plastics Piping Systems for Renovation of Underground Drainage and Sewerage Networks Under Pressure
Part 1: General; Part 3: Lining with close-fit pipes
🛠️ BS EN ISO 11297 specifies requirements for the renovation of pressurised underground drainage and sewerage networks using plastics piping systems, an important standard in trenchless pipeline rehabilitation. The series is organised into parts by renovation technique; this batch includes: BS EN ISO 11297-1 covering General requirements, and BS EN ISO 11297-3 covering renovation by lining with close-fit pipes. As underground networks age, trenchless rehabilitation — with less excavation, less traffic disruption and shorter time — is being widely adopted, and this Standard provides a unified technical basis.
💡 Trenchless renovation (CIPP, lining, pipe bursting, etc.) avoids large-scale excavation, reducing impact on traffic, the environment and adjacent buildings. Renovation of pressurised networks must consider both structural loading (internal and external pressure) and sealing; the Standard sets systematic requirements for materials, design and installation.
1. Series Overview and Scope 📌
In the UK this series is the responsibility of subcommittee PRI/88/3 (Rehabilitation of pipeline systems using plastics piping materials and components), prepared by ISO/TC 138 “Plastics pipes, fittings and valves for the transport of fluids” with CEN/TC 155 “Plastics piping systems and ducting systems”. BS EN ISO 11297-1:2013 was approved by CEN in April 2013 and published as a British Standard on 31 May 2013; BS EN ISO 11297-3:2013 was approved by CEN in June 2013 and published on 28 February 2014 (with a corrigendum of 28 February 2014 implementing the ISO corrected text of 1 August 2013).
| Part | Subject | ICS | ISO Equivalent | Technique |
|---|---|---|---|---|
| BS EN ISO 11297-1:2013 | General | 23.040.45; 23.040.20 | ISO 11297-1:2013 | General requirements for renovation of pressurised networks |
| BS EN ISO 11297-3:2013 | Lining with close-fit pipes | 23.040.45; 23.040.20 | ISO 11297-3:2013 | Renovation by lining with close-fit pipes |
⚠️ This series applies to the renovation of pressurised underground drainage and sewerage networks. For non-pressurised (gravity) networks, refer to the corresponding non-pressurised renovation standards (e.g., ISO 11298 series).
2. General (Part 1) 🔧
BS EN ISO 11297-1 specifies the general requirements for renovating pressurised underground drainage and sewerage networks with plastics piping systems, covering terms and definitions, piping-system materials, design principles, pre-construction survey (pipe-condition assessment), method selection, installation and acceptance requirements, and quality assurance and documentation. The Standard establishes a complete framework for renovation projects from preliminary survey, design and construction to acceptance.
The General part stresses that renovation should be based on a condition survey: CCTV, internal inspection and structural assessment determine the condition of the existing pipe (defect type, deformation, leakage); the renovation technique and liner structure are then chosen accordingly. The renovated system must meet pressurised operation, sealing and structural-safety requirements, with the specified service life.
3. Lining with Close-Fit Pipes (Part 3) 🔩
BS EN ISO 11297-3 specifies requirements for renovation using close-fit pipes. The close-fit lining technique reduces the cross-section of a prefabricated plastics liner pipe (e.g., folded or deformed pipe) mechanically or thermally, pulls it into the existing pipe, then restores the circular shape so it fits closely against the existing wall, forming a new pressurised liner. It suits existing pipes of relatively regular diameter and preserves a large effective flow area.
The Standard specifies the material, dimensions, structure, joining, installation equipment and procedures of the liner, and the pressure test and seal verification after installation. Whether an annular gap remains or the liner directly contacts the host pipe, the structural design and material must withstand internal and external (groundwater) pressure without failure.
| Comparison | General (Part 1) | Close-Fit Lining (Part 3) |
|---|---|---|
| Main content | General requirements and project framework | Specific requirements for close-fit liner pipes |
| Stages covered | Survey, design, construction, acceptance | Liner material, installation and testing |
| Typical materials | Various plastics piping systems | PE, PP and other thermoplastic liners |
| Typical use | All renovation techniques | Regular diameters, preserve flow area |
4. Materials, Design and Installation Requirements 🛠️
Design of a pressurised renovated piping system should consider internal pressure, external pressure (groundwater and soil load), temperature, medium and service life. Liner materials must meet internal-pressure, external-pressure, corrosion and creep-resistance requirements, evaluated through long-term hydrostatic strength (MRS/strength class) and ring stiffness. The Standard sets explicit requirements for material selection, structural design and installation quality.
- Material properties: meet pressure, corrosion and long-term creep requirements per the relevant material standard.
- Structural design: design wall thickness and ring stiffness for internal pressure and external loads.
- Installation control: control the pull-in/reduction process to avoid damaging the liner.
- Acceptance testing: perform pressure and seal tests after installation to confirm no leakage.
5. Engineering Application Practice 🌐
Renovation of pressurised drainage and sewerage networks is widely used in municipal utilities, industrial areas, sewage lifting and pressurised water-transmission systems. When an existing pipe suffers damage, leakage, deformation or reduced capacity, trenchless renovation restores function and extends life with significantly lower social cost than open-cut replacement. Before implementation, carry out a detailed pipe-condition survey and structural assessment, select the appropriate technique, and make good temporary drainage and flow-control arrangements to ensure construction safety and normal network operation.
🚨 If a renovated pressurised network leaks, it can cause sewage overflow, road settlement and environmental pollution. Renovation must strictly comply with pressure and seal verification, and must never be put into service without verifying sealing performance.
6. Frequently Asked Questions ❓
❓ Q: Why are pressurised and non-pressurised renovation standards separate?
A: Pressurised networks must withstand internal pressure, so liner structural design and sealing requirements differ from gravity networks. Pressurised renovation follows the ISO 11297 series; non-pressurised follows the ISO 11298 series.
A: Pressurised networks must withstand internal pressure, so liner structural design and sealing requirements differ from gravity networks. Pressurised renovation follows the ISO 11297 series; non-pressurised follows the ISO 11298 series.
❓ Q: What are the advantages of close-fit liner pipes?
A: Close-fit liners preserve a large effective flow area, withstand internal and external pressure after installation, suit existing pipes of regular diameter, and are prefabricated thermoplastics offering fast, quality-controlled installation.
A: Close-fit liners preserve a large effective flow area, withstand internal and external pressure after installation, suit existing pipes of regular diameter, and are prefabricated thermoplastics offering fast, quality-controlled installation.
❓ Q: Why is a pipe-condition survey necessary before renovation?
A: A condition survey (CCTV, etc.) identifies the defect type, deformation, leakage and obstructions of the existing pipe — the basis for selecting the technique, designing the liner structure and estimating quantities, avoiding blind construction and failure.
A: A condition survey (CCTV, etc.) identifies the defect type, deformation, leakage and obstructions of the existing pipe — the basis for selecting the technique, designing the liner structure and estimating quantities, avoiding blind construction and failure.
❓ Q: How is a renovated pipeline accepted?
A: After installation, perform a pressure test and a seal test (e.g., water/air tightness), and inspect the liner’s appearance, connections and dimensions; where necessary re-inspect with CCTV to confirm no deformation, leakage or defects.
A: After installation, perform a pressure test and a seal test (e.g., water/air tightness), and inspect the liner’s appearance, connections and dimensions; where necessary re-inspect with CCTV to confirm no deformation, leakage or defects.