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BS EN ISO 11298 — Plastics Piping Systems for Renovation of Underground Water Supply Networks (General and Close-Fit Lining)
Plastics Piping Systems for Renovation of Underground Water Supply Networks — Part 1: General & Part 3: Lining with Close-Fit Pipes (2011)
📐 BS EN ISO 11298 is the British Standard implementing the European Standard for plastics piping systems used in the renovation of underground water supply networks. The standard was developed by ISO/TC 138 “Plastics pipes, fittings and valves for the transport of fluids”, taken over as a European standard by CEN/TC 155 “Plastics piping systems and ducting systems”, and published in the UK by BSI. The series comprises two parts in this batch: Part 1: General and Part 3: Lining with close-fit pipes, superseding the withdrawn BS EN 14409 series. It applies to the design and construction of trenchless renovation of buried water mains, branches and service lines, and serves as a key reference for pipe renewal and network rehabilitation in the water industry.
💡 The core value of trenchless renovation is that it avoids large-scale excavation: a plastics liner is inserted, folded, or reduced in diameter and then restored to shape inside the existing pipe, rebuilding the inner lining of the conduit while preserving the host pipe, with lower social cost, shorter schedules, and much less disruption to traffic and residents.
1. Scope and Overview of the Series 📌
BS EN ISO 11298 is directed at the renovation of buried water supply networks and specifies general requirements, material selection, design criteria, installation practice, quality control, and acceptance methods for plastics piping systems used in renovation works. Each part of the series can be used independently, yet together they form a complete technical framework. Part 1 provides the general provisions, terms and definitions, symbols and abbreviations applicable to the whole series, together with the classification of renovation methods and selection principles. Part 3 gives dedicated requirements for the close-fit lining technique.
The renovation objects covered are buried water distribution networks conveying drinking water, made of plastics or metals. The renovated pipe must still satisfy water conveyance, hygienic safety, and structural load requirements. The standard therefore emphasizes the fit between the renovation system and the host pipe, the structural performance of the liner, and the long-term reliability of the renovated section.
⚠️ Note carefully that BS EN ISO 11298 addresses plastics renovation systems for water supply networks only, and differs significantly from the BS EN ISO 11299 series for gas networks in terms of media, safety, and hygiene requirements. The two must never be used interchangeably in engineering selection.
2. Series Structure and Technical Highlights 🔧
| Part | Standard No. | Title | Main Content |
|---|---|---|---|
| Part 1 | BS EN ISO 11298-1:2011 | General | Terms, symbols, classification of renovation methods, general design principles, material and system requirements, quality control foundations |
| Part 3 | BS EN ISO 11298-3:2011 | Lining with close-fit pipes | Materials, dimensions, installation process, reduction and reversion, connections, testing and acceptance of close-fit liners |
The series follows a “general part plus specific technique part” structure: Part 1 establishes the common framework, while the later parts give detailed provisions for particular renovation technologies (such as close-fit lining, CIPP, and other lining methods). This batch includes the general part and the close-fit lining part; other renovation technique parts are covered by the corresponding standards.
3. Key Technical Requirements 🔥
3.1 Materials and system performance
The plastics piping system used for renovation must satisfy both hygienic conveyance and structural strength requirements. The liner material (thermoplastics such as PE, PVC, and PP) must have sufficient long-term hydrostatic strength, corrosion resistance, and hygienic compliance. System design must account for the condition of the host pipe, groundwater pressure, and traffic loads, as well as the internal pressure requirements after renovation.
3.2 The close-fit lining technique
Close-fit lining is a technique in which a plastics liner is reduced in cross-section, pulled into the host pipe, and then restored to conform closely to the host pipe wall. Common implementation methods include the fold-and-form method, in which the pipe is folded into a U or C shape for insertion; reduction methods (rolldown / swagelining), in which the pipe is temporarily reduced in diameter by mechanical means; and heat reversion / memory-reversion methods. After installation the liner fits tightly against the original pipe with virtually no annular gap.
3.3 Design and installation control
The standard sets requirements for minimum liner wall thickness, reduction ratio, reversion recovery ratio, allowable bending radius, pulling load, connections, and end treatments. Prior to installation, CCTV inspection should be carried out to assess the condition of the host pipe; during installation, pulling speed and lubrication must be controlled; after installation, pressure testing and final inspection confirm that the renovated section is leak-free, wrinkle-free, and round.
✅ Key to acceptance: after installation the renovated section must pass hydrostatic (or air) tightness tests to verify overall sealing, and CCTV re-inspection to verify liner appearance and connection quality. The section may only be put into service when both structural integrity and hygienic safety requirements are met.
4. Engineering Practice Essentials 🛠️
- 🔍 Pre-assessment: use CCTV, hydraulic testing and structural assessment to determine the type and severity of host pipe defects and decide whether close-fit lining is suitable.
- 🔧 Material matching: select the thermoplastic liner according to the conveyed medium, water temperature, pressure class and site conditions, and verify hygiene approval and long-term strength.
- 📊 Installation execution: arrange temporary water shutdown and traffic diversion, control pulling load and reduction amount, and avoid scratching or excessive deformation of the liner.
- 📋 Quality acceptance: carry out the tests required by the standard and issue CCTV reports and pressure test records as the basis for handover.
5. Frequently Asked Questions ❓
❓ Q: What is the difference between BS EN ISO 11298 and BS EN ISO 11299?
A: They share a similar structure, but BS EN ISO 11298 covers water supply networks while BS EN ISO 11299 covers gas networks. Water systems emphasize hygiene safety and compliance of materials in contact with drinking water, while gas systems emphasize leak tightness and fire/explosion prevention — the technical requirements differ completely.
A: They share a similar structure, but BS EN ISO 11298 covers water supply networks while BS EN ISO 11299 covers gas networks. Water systems emphasize hygiene safety and compliance of materials in contact with drinking water, while gas systems emphasize leak tightness and fire/explosion prevention — the technical requirements differ completely.
❓ Q: How does close-fit lining differ from CIPP lining?
A: Close-fit lining uses pre-formed plastics pipe that reverts to shape against the host pipe wall, forming an independent pipe; CIPP (cured-in-place pipe) inverts or pulls in a resin-impregnated felt tube that cures into a monolithic lining. Close-fit is faster and pre-fabricated; CIPP has greater adaptability and can renovate irregular shapes and bends.
A: Close-fit lining uses pre-formed plastics pipe that reverts to shape against the host pipe wall, forming an independent pipe; CIPP (cured-in-place pipe) inverts or pulls in a resin-impregnated felt tube that cures into a monolithic lining. Close-fit is faster and pre-fabricated; CIPP has greater adaptability and can renovate irregular shapes and bends.
❓ Q: Can the renovated pipe carry the original design pressure?
A: The load capacity after renovation depends on liner wall thickness, material strength, and the residual structure of the host pipe. Structural design calculations per the standard are required, and verification by testing may be necessary to ensure the design internal pressure and external loads are satisfied.
A: The load capacity after renovation depends on liner wall thickness, material strength, and the residual structure of the host pipe. Structural design calculations per the standard are required, and verification by testing may be necessary to ensure the design internal pressure and external loads are satisfied.
🔍 Q: Why does the series only include the general part and the close-fit part?
A: This reflects the batch of documents published by BSI. The other renovation technique parts (such as CIPP and spiral winding) are specified in the corresponding ISO/EN standards; this article covers only the general part and the close-fit lining part in the collection.
A: This reflects the batch of documents published by BSI. The other renovation technique parts (such as CIPP and spiral winding) are specified in the corresponding ISO/EN standards; this article covers only the general part and the close-fit lining part in the collection.