ISO 21003-2:2008

Overview - ISO 21003-2:2008 (Multilayer pipes)

ISO 21003-2:2008 is the ISO product standard that specifies the characteristics and test parameters for pipes used in multilayer piping systems for hot and cold water installations inside buildings. It applies to systems conveying water for domestic use (whether or not potable) and for heating systems, under the design pressures and temperatures defined for each application class. ISO 21003-2 is a reference product standard and is intended to be used together with the other parts of ISO 21003 (system, fittings, fitness-for-purpose and conformity guidance).

Key topics and technical requirements

The standard addresses the essential technical aspects of multilayer piping systems including:

• Materials and construction

  • Declaration of materials for each layer and layer function.
  • Stress-bearing polymer materials accepted: PB, PE-RT, PE‑X, PP, PVC‑C.
  • Clean own reprocessable material allowed; external recyclates prohibited.
  • Materials in contact with drinking water must comply with national potable water regulations.

• Geometrical and appearance requirements

  • Dimensional characteristics, smooth surfaces, clean cut ends, opacity limits for declared opaque pipes.

• Pressure and long-term strength

  • Procedures for determining long‑term pressure strength and design pressure strength for P‑type and M‑type multilayer pipes.
  • Use of recognized test methods and reference product standards for stress layers.

• Durability and integrity

  • Thermal durability tests for outer layers (oven ageing, elongation at break).
  • Strength of weld lines for metal/polymer (M‑type) pipes and delamination resistance.
  • Oxygen permeability requirements for barrier performance.

• Test methods and performance

  • Defines test parameters and references specific test standards (e.g., long-term hydrostatic strength, adhesion, oxygen permeability).

• Marking and documentation

  • Minimum marking requirements and manufacturer declarations for traceability and correct selection.

Practical applications and users

ISO 21003-2 is used by:

• Pipe and system manufacturers designing and certifying multilayer pipes
• Building services engineers, specifiers and architects selecting piping for potable water and heating systems
• Installers and contractors ensuring compliant products are used on-site
• Test laboratories and conformity assessors executing the referenced test methods
• Regulators and authorities referencing product characteristics for approvals

Typical applications include indoor plumbing, domestic hot and cold water distribution, heating circuits, and renovation projects where multilayer piping (polymer/metal combinations) is preferred for combined performance (pressure resistance, low oxygen permeation, dimensional stability).

Related standards

Relevant companion and reference documents include:

• ISO 21003-1, -3, -5, -7 (system, fittings, fitness for purpose, conformity guidance)
• ISO 15874-2, ISO 15875-2, ISO 15876-2, ISO 15877-2 (reference product standards for PP, PE‑X, PB, PVC‑C pipes)
• Test and calculation standards such as ISO 9080 (long‑term hydrostatic strength), ISO 17454/17455/17456 (multilayer test methods), ISO 10508 and ISO 13760.

Keywords: ISO 21003-2, multilayer piping systems, multilayer pipes, hot and cold water installations, PE-X, PE-RT, PVC‑C, pipe test methods, oxygen permeability, thermal durability.