Choosing the correct pipe diameter is one of the most critical decisions in any plumbing project. A pipe that is too small will cause pressure drop and insufficient flow, while a pipe that is too large will create unnecessary costs. SP Industries piping system – Israel’s leading multi-layer piping system – comes in diameters 16, 20, 25, and 32 mm for household use, and 40, 50, and 63 mm for large projects. This guide will help you choose correctly in accordance with the requirements of the Israeli standard SI 1205.1.
Quick Summary
- One consumption point → 16 mm pipe (½")
- 2–3 points → 20 mm pipe (½")
- 4–9 points → 25 mm pipe (¾")
- 10–16 points → 32 mm pipe (1")
- Maximum working pressure: 10 bar | Maximum temperature: 95°C
- Pipe exposed to sunlight → black only
What is SP pipe and why is it different?
SP piping is multi-layer piping that combines a cross-linked PEX layer with a central aluminum layer and adhesive layers. This unique structure gives the pipe the rigidity of metal together with the flexibility of plastic.
Layer structure:
- Outer layer – cross-linked polyethylene
- Adhesive layer
- Central layer – aluminum
- Adhesive layer
- Inner layer – cross-linked polyethylene
The result: thermal expansion of only 2.5 mm per meter – compared with 15 mm in regular PEX pipes. This makes direct installation on the wall possible without additional conduits.
Pipe diameter selection table according to SI 1205.1
| Number of consumption points | Location | Minimum diameter (mm) | Galvanized equivalent |
|---|---|---|---|
| 1 | Anywhere | 16 mm | ½" |
| 2–3 | In the same bathroom or in separate rooms | 20 mm | ½" |
| 4–9 | Anywhere | 25 mm | ¾" |
| 10–16 | Anywhere | 32 mm | 1" |
Full technical specifications of SP pipes
| Pipe | Outer diameter | Wall thickness | Inner diameter | Water volume per 1 meter | Weight per 1 meter |
|---|---|---|---|---|---|
| 16×2 | 16 mm | 2.0 mm | 12 mm | 0.113 liters | 110 g |
| 20×2 | 20 mm | 2.0 mm | 16 mm | 0.201 liters | 145 g |
| 25×2.5 | 25 mm | 2.5 mm | 20 mm | 0.314 liters | 210 g |
| 32×3 | 32 mm | 3.0 mm | 26 mm | 0.530 liters | 340 g |
Reels: all sizes are supplied in 50-meter reels.
Important: Pipe exposed to sunlight
Any SP pipe installed in an area exposed to sunlight must be black only. Colored pipes (blue, orange, white) are not suitable for outdoor installation.
Large diameters: 40, 50 and 63 mm
For large projects – public buildings, hotels, high-rise buildings, and central solar systems – SP Industries supplies pipes in large diameters:
| Diameter | Wall thickness | Supply length | Item no. | Price per m |
|---|---|---|---|---|
| 40×3.5 | 3.5 mm | 3.5 m rods (white) | 7700113 | 57 ₪ |
| 50×4 | 4.0 mm | 5 m rods | 7700121 | 86 ₪ |
| 63×4.5 | 4.5 mm | 5 m rods | 7700131 | 154 ₪ |
Note: the 40 mm pipe is supplied in white and in 3.5 m rod length only – unlike the 50 and 63 diameters, which are supplied in 5 m lengths.
Tip: Insulated pipe for energy savings
For hot water, it is recommended to use insulated SP pipes (6 mm insulation, black color). They are supplied in diameters 16, 20, 25, and 32 mm and prevent heat loss לאורך the piping. Never place a cold pipe next to a hot pipe – maintain a minimum spacing of 3 cm.
Internal water volume calculator
When you need to know how much water the pipe holds (for pressure testing, flushing, or system design), you can calculate it easily:
Formula: Volume (liters) = volume per 1 meter × pipe length (m)
Examples:
- 16 mm pipe with a length of 10 m = 0.113 × 10 = 1.13 liters
- 25 mm pipe with a length of 20 m = 0.314 × 20 = 6.28 liters
- 32 mm pipe with a length of 15 m = 0.530 × 15 = 7.95 liters
Frequently asked questions about choosing SP pipe diameter
What is the difference between 16 and 20 mm pipe?
A 16 mm pipe is suitable for a single consumption point. A 20 mm pipe is required when there are 2–3 consumption points in the same bathroom or in separate rooms – according to the requirements of SI 1205.1.
Can a 25 mm pipe be used for 9 consumption points?
Yes. According to the table, 4–9 consumption points anywhere require a minimum diameter of 25 mm (¾"). Only from 10 points and above is a 32 mm pipe required.
What is the maximum working pressure of SP pipe?
Maximum working pressure: 10 bar. Maximum operating temperature: 95°C.
Is SP pipe suitable for underfloor heating?
Yes, but only the red SP 16×2 pipe is intended for underfloor heating. It is supplied in 120, 240, or 300 meter reels.
What is the minimum bending radius?
According to SI 1205.1: 16 mm → 80 mm | 20 mm → 100 mm | 25 mm → 125 mm | 32 mm → 320 mm (10 times the diameter).
Conclusion
Choosing the correct pipe diameter is the foundation of any proper plumbing system. With the table from SI 1205.1 and the SP piping specifications, you can plan with confidence – whether it’s a small apartment with one point or a high-rise building with dozens of consumption points. For additional questions, our Pipe Diameter Selection tool will calculate the exact recommendation in seconds.