SDR and pressure rating for PE100 pipe

The two numbers are the same fact, written differently

SDR is outside diameter divided by wall thickness. A lower SDR means a thicker wall. PN is the nominal pressure in bar at 20 °C and follows from the wall:

PN = 2 × σs × 10 / (SDR − 1), σs = MRS / C

For PE100 water pipe (MRS 10 MPa, C 1.25 → σs 8 MPa) this gives the familiar pairs: SDR26 = PN6, SDR17 = PN10, SDR13.6 = PN12.5, SDR11 = PN16, SDR9 = PN20, SDR7.4 = PN25.

Temperature, and what it does to the number

PN is defined at 20 °C. Above that the allowable stress drops, so the same pipe holds less pressure. Derating factors are published by the resin supplier; for water service the usual order is roughly 0.87 at 30 °C and 0.74 at 40 °C.

Two practical consequences: a PN10 line carrying warm water may need SDR13.6 or SDR11, and a line with pump surge should be specified one class up regardless of the static head.

How to read it on a drawing

• “DN315 PE100 SDR17” fixes OD 315 and wall ≈ 18.5 mm → PN10
• If the drawing says only “PN10”, the SDR is implied by the material
• PE80 at the same SDR gives a lower PN — check the material, not just the SDR
• Weight per metre is what your freight and lifting plan needs, not the OD

Where this table stops

Above OD630 the wall thickness table changes shape and SDR33/SDR41 appear for low-pressure irrigation and gravity work. Those sizes are quoted per order — send the diameter and the pressure and we return the datasheet rather than extrapolating.