BS 1387 vs ASTM A53 Galvanized Pipe: Which Standard Should You Order?

2026-09-24 · Pipe & Tube · 3 min read

Two galvanized pipes can have the same nominal size, the same zinc finish and nearly the same price, and still not fit together on site. The reason is usually the standard. Across Africa, the Middle East and Southeast Asia, most tenders call for either BS 1387 (now EN 10255) or ASTM A53. This guide explains how the two differ and how to order the right one.

Where each standard comes from

BS 1387 is the British standard for screwed and socketed steel tubes for water, gas and air. It was formally replaced by EN 10255 in 2004, but the name is still used everywhere in former British markets: Nigeria, Ghana, Kenya, Tanzania, Uganda, Zambia, the UAE, Qatar, Oman and much of South Asia. Many specifications still say "BS 1387 Medium", and suppliers deliver EN 10255 Medium, which has near-identical dimensions.

ASTM A53 is the American standard for welded and seamless steel pipe, black or galvanized, for pressure and mechanical use. It dominates in the Philippines, Saudi Arabia (alongside other standards), Latin America and any project designed by US consultants. Sizes follow the ASME B36.10 schedule system.

Wall thickness: classes vs schedules

BS 1387 uses three weight classes, Light, Medium and Heavy, identified by coloured bands (brown, blue and red). ASTM A53 uses schedules, mainly SCH40 (standard weight) and SCH80 (extra strong). The outside diameters are almost the same, but the walls are not:

(All walls in mm.) At small sizes, SCH40 falls between Medium and Heavy. At 4 inch it is much heavier than BS Heavy. Because pipe is priced per ton, a 4" SCH40 pipe costs noticeably more per metre than BS Medium. That matters when you compare quotations: check the wall thickness, not only the price per ton.

Threads are not interchangeable

This is the most expensive mistake we see. BS 1387 / EN 10255 pipe is threaded to BSPT (ISO 7 / BS 21, a 55° thread form). ASTM A53 pipe for threaded service uses NPT (ASME B1.20.1, 60° thread form), and from 1" upward the pitch differs as well (11 threads per inch for BSPT against 11.5 for NPT). A BSPT fitting will screw onto an NPT pipe for a turn or two and then leak. Always buy fittings, valves and pipe threaded to the same system.

Zinc coating

Both standards allow hot-dip galvanizing after the pipe is made. BS/EN pipe is galvanized to EN 10240, and ASTM A53 sets its own minimum zinc weight for galvanized pipe. In practice, good mills apply around 400–550 g/m² in both cases. What really matters is ordering hot-dip galvanized rather than pre-galvanized pipe for water service. Pre-galvanized pipe has a thin coating and an unprotected weld line inside. For a full comparison see our galvanized steel pipe page.

Testing and markings

• BS 1387 / EN 10255: each pipe is hydrostatically tested (typically 50 bar) or eddy-current tested, and marked with the standard, class and manufacturer.
• ASTM A53: hydrostatic test pressure depends on size and schedule. Pipe is marked with grade (A or B), type (E = ERW, S = seamless), size and schedule.

For government and utility tenders, ask for a mill test certificate to EN 10204 3.1 and, where required, a third-party inspection report. Nigerian imports also need SONCAP documentation, and Saudi imports SASO / SABER certificates, so plan these before shipment.

Which should you order?

1. Follow the drawings. If the consultant names a standard and class, order exactly that.
2. Match the existing network. On a repair or extension, check the thread type of the installed fittings.
3. Stocking for resale? Stock what local plumbers ask for. In East and West Africa and the Gulf that is usually BS 1387 Medium with BSPT threads; in the Philippines it is usually SCH40 with NPT.
4. Structural use (fencing, scaffolding, frames) does not need a pressure-pipe standard. EN 10219, ASTM A500 or GB/T 3091 pipe is cheaper and works well.

Frequently asked questions