HDPE pipe is specified by three things: its outside diameter (OD) in mm, its material grade (PE100 is today’s standard), and its SDR, which sets the pressure rating. This guide shows how they fit together so you can order the right pipe the first time.
What SDR means
SDR (standard dimension ratio) is the outside diameter divided by the wall thickness. A lower SDR means a thicker wall and a higher pressure rating.
Wall thickness = OD ÷ SDR. For example, 110mm SDR11 pipe has a 10mm wall.
PE100 SDR to pressure (PN) chart
Pressure ratings below are for PE100 water pipe at 20°C, to SANS ISO 4427.
| SDR | Pressure rating | Typical use |
|---|---|---|
| SDR 26 | PN6 (6 bar) | Low-pressure and gravity lines |
| SDR 21 | PN8 (8 bar) | Irrigation and low-pressure reticulation |
| SDR 17 | PN10 (10 bar) | Water reticulation, mine water and dewatering lines |
| SDR 13.6 | PN12.5 (12.5 bar) | Medium-pressure mains |
| SDR 11 | PN16 (16 bar) | Pumping mains, high-pressure process and mine lines |
| SDR 9 | PN20 (20 bar) | High-pressure lines |
| SDR 7.4 | PN25 (25 bar) | Very high-pressure lines |
Common sizes and wall thickness
| OD | SDR 17 (PN10) wall | SDR 11 (PN16) wall |
|---|---|---|
| 63mm | 3.8mm | 5.8mm |
| 110mm | 6.6mm | 10.0mm |
| 160mm | 9.5mm | 14.6mm |
| 200mm | 11.9mm | 18.2mm |
Temperature
PN ratings apply at 20°C. At higher water temperatures the allowable pressure drops, so pick a lower SDR (thicker wall) for warm process water. Ask us for derating values for your operating temperature.
Joining HDPE pipe
- Butt fusion: pipe ends heated and pressed together; strong and leak-free, used on most mine and municipal lines.
- Electrofusion: couplers with built-in heating wire; ideal for repairs and tight spaces.
- Compression fittings: quick mechanical joints for smaller sizes, typically up to 110mm.
- Stub flange and backing ring: connects HDPE to pumps, valves and steel pipe. Backing rings are drilled to SANS 1123, commonly Table 1000/3 (PN10) or 1600/3 (PN16).
How to order
- Outside diameter (mm)
- SDR or pressure class (e.g. SDR17 / PN10)
- Length: 6m or 12m lengths, or coils for small sizes
- Ends: plain, or stubbed and flanged (state the flange table)
Shop HDPE pipe → or send your pipe schedule to info@syre.co.za for a quote. Same-day delivery in Gauteng and Mpumalanga on orders placed before 12pm, and delivery to other provinces across South Africa.
