ISO 21138-3:2020

Overview - ISO 21138-3:2020 (structured-wall piping systems, Type B)

ISO 21138-3:2020 defines requirements for structured-wall piping systems made from unplasticized poly(vinyl chloride) (PVC‑U), polypropylene (PP) and polyethylene (PE) intended for non‑pressure underground drainage and sewerage. Part 3 covers pipes and fittings with a non‑smooth external surface and a smooth internal surface (Type B). The standard sits alongside ISO 21138‑1 and is applicable to socketed elastomeric ring joints as well as welded and fused joints. It also provides guidance for larger dimensions (greater than DN/OD 1200 or DN/ID 1200).

Key technical topics and requirements

• Materials: Requirements and characteristics for PVC‑U, PP and PE materials, including guidance on use of virgin, reprocessed and recycled material (normative annexes).
• Wall construction: Definition and designation of Type B structured‑wall constructions (e.g., ribbed or corrugated external profiles).
• Joints and jointing methods: Compatibility and dimensional requirements for elastomeric ring seal joints, welded and fused joints; joint performance criteria.
• Geometrical characteristics: Dimensions, diameters, lengths, and wall thickness ranges for Type B pipes and fittings.
• Mechanical and physical characteristics: Tests and parameters for ring stiffness, ring flexibility, tensile strength of seams and other mechanical properties.
• Performance and test methods: Specified test methods and parameters to demonstrate compliance (referenced ISO test methods).
• Colour and marking: Recommendations on colours and minimum marking information for traceability and installation.
• Scope limitations: Covers a range of sizes, materials and nominal ring stiffnesses; purchasers/specifiers must select appropriate combinations for their installation practices or codes.

Practical applications and users

ISO 21138-3 is intended for:

• Civil engineers and designers specifying non‑pressure drainage and sewerage systems
• Manufacturers of structured-wall PVC‑U, PP and PE pipes and fittings
• Procurement specialists and public works authorities setting technical specs
• Site contractors and installers checking joint compatibility and performance
• Highway drainage and surface water management projects (standard notes suitability)

Practical benefits include clear criteria for material selection, joint compatibility, performance verification and interchangeability with components conforming to related plastics product standards.

Related standards

• ISO 21138‑1 - General requirements for structured‑wall piping systems (use in conjunction with Part 3)
• ISO 21138‑2 - Joint dimensions and other parts of the ISO 21138 series (referenced for joint compatibility)

Keywords: ISO 21138-3:2020, structured-wall piping systems, Type B, PVC-U, PP, PE, non-pressure underground drainage, elastomeric ring seal, ring stiffness, drainage pipe standard.