Search for “GI pipe sizes” in the Gulf and you will meet two different pipe standards that share the same nominal sizes: EN 10255 (the old BS 1387) with BSP threads, and ASTM A53 with NPT threads. The outside diameters are almost the same; the wall thickness and the thread are not. This page puts both side by side, with the TUPY fitting that screws onto each.
GI pipe sizes to EN 10255 / BS 1387 (BSP thread)
This is the pipe most often used for water, drainage and fire lines in the UAE, Qatar, Oman, Kuwait and Bahrain. It comes in three wall series – light, medium and heavy – with the same outside diameter, so the same fitting fits all three. Medium is the usual site specification.
| Size | DN | OD (mm) | Light wall (mm) | Medium wall (mm) | Heavy wall (mm) | BSP TPI |
|---|---|---|---|---|---|---|
| 1/2″ | 15 | 21.3 | 2.0 | 2.6 | 3.2 | 14 |
| 3/4″ | 20 | 26.9 | 2.3 | 2.6 | 3.2 | 14 |
| 1″ | 25 | 33.7 | 2.6 | 3.2 | 4.0 | 11 |
| 1.1/4″ | 32 | 42.4 | 2.6 | 3.2 | 4.0 | 11 |
| 1.1/2″ | 40 | 48.3 | 2.9 | 3.2 | 4.0 | 11 |
| 2″ | 50 | 60.3 | 2.9 | 3.6 | 4.5 | 11 |
| 2.1/2″ | 65 | 76.1 | 3.2 | 3.6 | 4.5 | 11 |
| 3″ | 80 | 88.9 | 3.2 | 4.0 | 5.0 | 11 |
| 4″ | 100 | 114.3 | 3.6 | 4.5 | 5.4 | 11 |
| 5″ | 125 | 139.7 | – | 5.0 | 5.4 | 11 |
| 6″ | 150 | 165.1 | – | 5.0 | 5.4 | 11 |
Threaded ends are BSP taper (R) to ISO 7 / EN 10226. TUPY BSP fittings are made to EN 10242 and fit every wall series above. See the BSP and NPT thread chart for pitch in mm.
GI pipe sizes to ASTM A53 Schedule 40 (NPT thread)
American-standard pipe is common in Saudi Arabia, in oil and gas facilities, and wherever the fire-protection design follows NFPA. It is threaded NPT, which is not interchangeable with BSP even where the outside diameter matches.
| Size | DN | OD (mm) | Sch 40 wall (mm) | NPT TPI |
|---|---|---|---|---|
| 1/2″ | 15 | 21.3 | 2.77 | 14 |
| 3/4″ | 20 | 26.7 | 2.87 | 14 |
| 1″ | 25 | 33.4 | 3.38 | 11.5 |
| 1.1/4″ | 32 | 42.2 | 3.56 | 11.5 |
| 1.1/2″ | 40 | 48.3 | 3.68 | 11.5 |
| 2″ | 50 | 60.3 | 3.91 | 11.5 |
| 2.1/2″ | 65 | 73.0 | 5.16 | 8 |
| 3″ | 80 | 88.9 | 5.49 | 8 |
| 4″ | 100 | 114.3 | 6.02 | 8 |
| 5″ | 125 | 141.3 | 6.55 | 8 |
| 6″ | 150 | 168.3 | 7.11 | 8 |
For NPT pipe use TUPY NPT figures: Class 150 for general water and fire lines, Class 300 for compressed air, steam and higher pressures – see Class 150 vs Class 300 fittings.
How to tell which pipe you have
- Read the stencil. GI pipe is marked with its standard – EN 10255, BS 1387 or ASTM A53 – and the series or schedule.
- Measure the wall. At 1″ and above, Schedule 40 walls are thicker than BS medium; a 2″ pipe with a 3.9 mm wall is ASTM, 3.6 mm is BS medium.
- Count the threads. From 1″ to 2″ BSP has 11 threads per inch and NPT 11.5; from 2.1/2″ up, BSP stays at 11 and NPT drops to 8.
Matching TUPY fittings by size
Fittings are ordered by nominal size and thread, not by wall thickness: a 1″ BSP elbow fits 1″ light, medium or heavy pipe. TUPY makes the full galvanised and black range from 1/8″ to 6″, for example NPT Class 300 elbows and NPT Class 300 tees. For galvanised fittings in the UAE see GI fittings supplier in the UAE; for other markets see Saudi Arabia, Qatar and Oman.
ABMT supplies TUPY fittings, not pipe. Buy the pipe from your local stockist and send us the size list and thread – we quote the matching fittings.
