Catalogue specifications for 20 mm polyethylene pipe.
20 mm HDPE pipe means pipe with a 20 mm outside diameter. That figure alone does not define an order — at this diameter the factory produces 4 different pressure classes, which differ in wall thickness and therefore in bore, weight and price. What completes an order is the diameter plus the SDR and the material grade.
At 20 mm, wall thickness ranges from 2 to 3.4 mm and nominal pressure from 12.5 to 25 bar, depending on the SDR and on whether the material is PE80 or PE100.
| SDR 11 | Wall thickness 2 mm — nominal pressure 12.5 bar in PE80, 16 bar in PE100 |
|---|---|
| SDR 9 | Wall thickness 2.3 mm — nominal pressure 16 bar in PE80, 20 bar in PE100 |
| SDR 7.4 | Wall thickness 3 mm — nominal pressure 20 bar in PE80, 25 bar in PE100 |
| SDR 6 | Wall thickness 3.4 mm — nominal pressure 25 bar in PE80 (the catalogue states no PE100 figure) |
Figures from the factory catalogue (DIN 8074 / ISO 4427-2). A lower SDR means a thicker wall, a higher pressure rating and a smaller bore.
The nominal pressure figure applies at 20 °C. If the line runs warmer, the real allowable pressure is lower and has to be calculated with the temperature derating factor.
20 mm also appears in the catalogue's drip irrigation table (ISO 8779), in PE32 and PE40 grades at lower pressure classes. That is not the same product as pressure water pipe.
