Overview
EN ISO 15876-3:2017/A2:2021 is Amendment 2 to Part 3 of the ISO 15876 series covering polybutene (PB) fittings for plastics piping systems used in hot and cold water installations. Endorsed by CEN in October 2021, this amendment updates definitions, test requirements and material/inspection provisions for both plastic and metallic fittings used with PB pipe systems.
Key topics and technical requirements
- Updated terms and definitions - clarified joint types: compression fitting, radial press fitting, and new definitions for axial press fitting and push‑fit fitting (including notes on internal supports and sealing elements).
- Metallic materials - metallic fittings for use with ISO 15876 components are limited to copper alloys or stainless steel alloys, to be defined by relevant standards or regulations.
- Appearance and dimensional checks:
- Plastic fittings: smooth, clean surfaces, perpendicular ends; dimensions measured per ISO 3126.
- Metal fittings: clean, burr‑free surfaces; dimensions measured per ISO 2768‑1 and/or ISO 22081.
- Minimum wall thickness - Annex A provides dimensional requirements for copper‑alloy fittings (minimum thickness at specified points), with measurement guidance.
- Material and performance testing:
- MFR/MVR (melt flow/mass‑volume flow) of PB compounds and molded fittings per ISO 1133‑1; for PB the MFR/MVR difference shall not exceed 30% under specified conditions.
- Stress corrosion resistance for copper‑alloy fittings; CuZn alloys are acceptable when hardness meets thresholds (HBW ≤110 or HV ≤134 as specified).
- Dezincification resistance (where declared) tested to ISO 6509‑1 with acceptance criteria: maximum depth ≤200 µm; average ≤100 µm.
- Tightness test for cast alloys - new Clause 12 requires leak testing of cast fittings after machining using compressed air at ≥ 0.5 MPa (5 bar) while immersed in water (air bubbles indicate leakage).
Applications and who uses it
This amendment is relevant for:
- Fittings manufacturers (design, production, QC)
- Plumbing system designers and specifiers using PB piping
- Test laboratories and conformity assessment bodies
- Installers and trade professionals selecting compatible fittings (compression, press, push‑fit)
- Regulators and standards bodies implementing national adoption (CEN members required to adopt by April 2022)
Related standards (examples)
This amendment improves clarity on joint types, materials, testing and dimensional controls - critical for ensuring safe, durable PB hot-and-cold water installations.