ISO 8361-2:1991

Overview

ISO 8361-2:1991 - Thermoplastics pipes and fittings - Water absorption - Part 2 specifies test conditions for determining water absorption of unplasticized poly(vinyl chloride) (PVC‑U) pipes and fittings. It complements the general method in ISO 8361‑1 and gives the detailed conditioning, immersion and measurement steps, plus an informative preferred maximum water absorption. This standard is essential for quality control, compliance testing and material selection for PVC‑U piping systems.

Key topics and requirements

• Reference standard: ISO 8361‑1:1991 (general test method). ISO 3126:1974 is cited for dimension measurement.
• Test principle: Condition test pieces, measure mass and surface area, immerse in boiling distilled water, re-measure mass and calculate mass change per unit area.
• Primary test steps (condensed):
  • Condition and measure test-piece dimensions and total surface area (per ISO 8361‑1).
  • Briefly immerse in acetic acid (1 min at 23°C ± 2°C), then in distilled water (1 h at 23°C ± 2°C).
  • Dry in desiccator (2 h at 23°C ± 2°C) and determine mass.
  • Immerse in boiling distilled water for 24 hours.
  • Cool in bath for 15 min ± 1 min (at 23°C ± 2°C), wipe, desiccate (2 h at 23°C ± 2°C), and determine final mass.
  • Calculate water absorption as mass gain per unit area and report results per ISO 8361‑1.
• Preferred maximum value (informative): Annex A indicates a preferred maximum water absorption of 40 g/m² after the specified test conditions.
• Scope limitation: Absorption values appropriate for specific applications are defined in relevant product standards; other PVC variants (PVC‑C, PVC‑HI) and related materials are covered in other or future parts.

Applications and users

• Who uses it: PVC‑U pipe and fitting manufacturers, independent testing laboratories, product certification bodies, specifiers, procurement teams, and regulatory authorities.
• Practical uses:
  • Routine quality control and batch testing for PVC‑U pipes and fittings.
  • Compliance testing to demonstrate material stability and suitability for intended fluid-transport applications.
  • Supporting product standards and technical specifications where water absorption limits influence long‑term performance and durability.
  • Informing material selection and design decisions for potable water, drainage and industrial piping systems.

Related standards

• ISO 8361‑1:1991 - Thermoplastics pipes and fittings - Water absorption - Part 1: General test method
• ISO 8361 (other parts) - Part 3: Test conditions for ABS pipes and fittings; additional parts planned for PVC‑C, PVC‑HI, ASA
• ISO 3126:1974 - Plastics pipes - Measurement of dimensions

Keywords: ISO 8361‑2, PVC‑U, water absorption test, thermoplastics pipes, test conditions, pipe fittings, ISO 8361.