What is a GI pipe?
A GI (galvanized iron) pipe is a mild steel pipe with a zinc coating that protects the steel from rust. GI pipes are widely used for water supply, fire-fighting lines, compressed air, scaffolding, fencing, greenhouses and general structural work. See our GI pipe range for sizes and pricing guidance.
Light, medium and heavy class
IS 1239 (Part 1) groups tubes by wall thickness into light (A), medium (B) and heavy (C) classes. Medium is the usual choice for water and general piping; heavy is selected for higher pressure, threading and rough service.
GI pipe size and weight chart
| Nominal bore | Outside dia (mm) | Light: wall mm / kg per m | Medium: wall mm / kg per m | Heavy: wall mm / kg per m |
|---|---|---|---|---|
| 15 mm | 21.3 | 2.0 / 0.95 | 2.6 / 1.20 | 3.2 / 1.43 |
| 20 mm | 26.9 | 2.3 / 1.40 | 2.6 / 1.56 | 3.2 / 1.87 |
| 25 mm | 33.7 | 2.6 / 1.99 | 3.2 / 2.41 | 4.0 / 2.93 |
| 32 mm | 42.4 | 2.6 / 2.55 | 3.2 / 3.09 | 4.0 / 3.79 |
| 40 mm | 48.3 | 2.9 / 3.25 | 3.2 / 3.56 | 4.0 / 4.37 |
| 50 mm | 60.3 | 2.9 / 4.11 | 3.6 / 5.03 | 4.5 / 6.19 |
| 65 mm | 76.1 | 3.2 / 5.75 | 3.6 / 6.44 | 4.5 / 7.95 |
| 80 mm | 88.9 | 3.2 / 6.76 | 4.0 / 8.38 | 4.8 / 9.96 |
| 100 mm | 114.3 | 3.6 / 9.83 | 4.5 / 12.19 | 5.4 / 14.50 |
Note: Values are indicative, with weights calculated theoretically for plain steel. Mill tolerances and the zinc coat change actual weight. Confirm thickness against the latest IS 1239 (Part 1) before ordering.
GI pipe vs MS pipe
| Point | GI pipe | MS (black) pipe |
|---|---|---|
| Coating | Zinc galvanized | None (plain or oiled) |
| Corrosion resistance | High, suited to outdoor and wet use | Low, needs paint |
| Best for | Water lines, fencing, scaffolding, greenhouses | Structures that will be painted, welded frames |
| Welding | Possible but coating must be restored | Easy |
How to select GI pipe
- Pick the nominal bore from the flow or structural need.
- Choose the class (light, medium, heavy) based on pressure and joining method.
- State the length (usually 6 m) and any threading or sockets.
- Mention the quantity and delivery city.
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