ISO 21004:2006

Overview

ISO 21004:2006 - "Plastics piping systems - Multilayer pipes and their joints, based on thermoplastics, for water supply" defines general and performance requirements for multilayer thermoplastic pipes and their joints used in water supply outside buildings. The standard covers design guidance for piping systems where at least 60% of wall thickness is polymeric and the inner water-contact layer is polymeric. It applies to buried mains, service pipes and above-ground systems conveying cold drinking water (≈20 °C) and water up to 40 °C for general purposes.

Key topics and technical requirements

• Material selection: Stress-bearing polymeric layers may include polybutylene (PB), polyethylene (PE), crosslinked PE (PE-X), polypropylene (PP), PVC-C and PVC-U. PE-RT and PE-X are treated consistently with thermoplastics in this context.
• Design guidance: Requirements and calculation/testing procedures for system design, including design coefficients and PN ranges for pressure ratings.
• Long-term hydrostatic strength (LTHS): Methods for determining long-term pressure performance (calculation and testing approaches).
• Geometry and dimensions: Specified dimensional controls and ring stiffness/ring flexibility considerations.
• Mechanical characteristics: Pressure performance control points, structural performance and fitness-for-purpose tests.
• Jointing techniques and testing: Guidance and test methods for mechanical fittings, electrofusion and butt-fusion joints, pull-out and leaktightness tests, and specific jointing requirements for multilayer constructions.
• Fitness for purpose: System-level evaluation including fittings, valves and ancillary components to ensure end-to-end performance.
• Marking and documentation: Requirements for product identification and traceability.
• Annexes: Normative lists and helpful procedures, e.g., reference product standards, design coefficient application, PE saddle tear tests and pressure reduction coefficients.

Applications and users

ISO 21004 is intended for:

• Pipe manufacturers developing multilayer thermoplastic products for water distribution
• System designers and engineers specifying pipe constructions, pressure ratings and jointing methods
• Water utilities and infrastructure owners requiring validated products for buried mains and services
• Testing laboratories and certification bodies conducting LTHS, joint and fitness-for-purpose tests
• Regulators and procurement teams setting performance-based specifications

Benefits include consistent material selection, validated jointing techniques, predictable long-term performance and improved compatibility across multilayer pipe systems.

Related standards

ISO 21004 references and complements many ISO product and test standards, for example:

• ISO 4427 (PE water supply systems), ISO 15875 (PE-X), ISO 15874 (PP), ISO 15876 (PB), ISO 4422 (PVC-U)
• Test and design standards: ISO 1167 (internal pressure), ISO 9080 (LTHS), ISO 9969 (ring stiffness), and several jointing standards (e.g., ISO 13953, ISO 13954)

Keywords: ISO 21004:2006, multilayer pipes, thermoplastics, water supply, PE, PE-X, PP, PB, PVC-U, joints, long-term hydrostatic strength, piping system design.