ISO 4427

Covers — polyethylene (PE) piping systems for water supply and pressure drainage/sewerage: PE80/PE100 pipes, fittings, valves, and system fitness-for-purpose, dimensioned by PN and SDR (multi-part standard).

Does NOT cover (exclusions) — the following are governed elsewhere:

• North American OD/DR-based PE pipe → ASTM D3035 / F714; US waterworks PE → AWWA C906.
• The Thai national HDPE standard → TIS 982-2556.
• Non-pressure/gas PE distribution → separate ISO/EN gas standards.

PE rating is the combination of material grade (MRS) and SDR — always state both PN and SDR.

ISO 4427 sets minimum requirements for PE water pipe:

• Material — PE80/PE100 compounds classified by minimum required strength (MRS).
• Dimensions — pipe OD and wall thickness by SDR, with tolerances.
• Pressure Rating (PN) — derived from MRS, SDR, and design coefficient for water at 20 °C.
• Testing — hydrostatic (long-term), tensile, and system fitness-for-purpose tests; fusion-jointing suitability.

ISO 4427 is the leading international standard for polyethylene (PE) water pipe. It is published in five parts: Part 1 (general), Part 2 (pipes), Part 3 (fittings), Part 4 (valves), and Part 5 (fitness for purpose of the system).

How PE pipe is rated

Pressure rating combines the material grade with the wall thickness. The grade is captured by its Minimum Required Strength (MRS) — PE80 → MRS 8.0 MPa, PE100 → MRS 10.0 MPa — and the wall by the Standard Dimension Ratio, SDR = OD ÷ wall thickness. The allowable pressure follows:

PN = 20 · MRS / [ C · (SDR − 1) ], with design coefficient C = 1.25 for water at 20 °C.

A lower SDR (thicker wall) gives a higher PN. The common series:

PN in bar, for water at 20 °C over a 50-year design life (C = 1.25). Confirm against the current ISO 4427-2 dimension tables for your grade and OD.

Temperature derating

Ratings assume 20 °C water. Above this the allowable pressure must be derated — use the manufacturer's / ISO temperature-reduction factors (PE is not suitable for hot-water service; typical continuous limit is around 40 °C).

Jointing

PE is joined chiefly by butt fusion and electrofusion, not adhesive, so joint reliability hinges on qualified fusion procedures (WIS / ISO 21307 style) and trained operators. Transitions to flanges use stub ends with backing rings; mechanical compression couplings are used for small bores and repairs.

The Thai TIS 982 and US AWWA C906 cover the same material in their national frameworks.

Engineering Note: Always specify both the material grade and the SDR (e.g., PE100 SDR11) — quoting only "PE100" or only a PN without the SDR leaves the wall thickness and true rating ambiguous.