What is GI galvanized pipe?
GI galvanized pipe is round steel pipe formed from pre-galvanized (zinc-coated) coil: the coated strip is slit, rolled into a tube and welded, and the weld seam is sprayed with zinc. The zinc layer is thinner than on hot-dip galvanized (HDG) pipe, so GI costs less. It is the go-to galvanized steel pipe for posts, tent frames, fences, railings and light structures. We stock 1/2–6 in, 1.4–3.2 mm wall, 6 m lengths.
GI vs HDG pipe: what's the difference?
Thailand has two kinds of galvanized pipe, so say which one you need before you order. GI pipe is formed from zinc-coated coil. HDG pipe is formed from black coil and then dipped in a zinc bath. GI has the thinner coating and lower price; HDG lasts longer.
GI pipe | HDG pipe | |
|---|---|---|
How it's made | Pre-galvanized (zinc-coated) coil formed into pipe | Black steel pipe hot-dip galvanized after forming |
Zinc layer | Thinner | Thicker, inside and outside |
Price | Lower | Higher |
TIS standard | TIS 107-2566 structural pipe (plain ends) | TIS 276-2562 water pipe (plain and threaded ends) |
Best for | Posts, tent frames, fences, structures, temporary work | Water supply systems, outdoor work, long service life |
Can GI pipe be used for water lines?
For temporary use, yes, but it isn't recommended for a water system you'll rely on for years.
- Water supply systems: choose HDG pipe. It lasts longer and doesn't need replacing often.
- A little garden watering or a temporary line: GI works, but it won't last. Fine if you'll remove it later.
- Posts and tent frames: GI is the budget-friendly choice and does the job well.
GI pipe types
Type | Sizes | Wall | Best for |
|---|---|---|---|
Red stripe, plain ends | 1/2–2 in | 1.4 mm | Handrails, fences, light-duty work |
Yellow stripe Class S, threaded | 1/2–3 in | 1.4–2.1 mm | Tent frames, scaffolding, temporary water lines |
Blue stripe Class M, threaded | 1/2–4 in | 1.8–2.5 mm | Posts, structures, tent frames |
Plain ends, thick wall | 1.5–2.5 in | 2.3–3.2 mm | Structures, posts, roof frames |
Plain ends, TIS 107-2566 | 3–6 in | 2.3–3.2 mm | Structural work that calls for TIS pipe |
The colored stripe marks the wall class: red is the thinnest and can't be threaded, yellow Class S is thicker and factory-threaded, and blue Class M is thicker again.
Does GI pipe have a TIS standard?
Only plain-end round GI pipe, under TIS 107-2566, which is a structural pipe standard rather than a water pipe standard. Water pipe is covered by TIS 276-2562, which is HDG pipe; see HDG pipe TIS 276-2562.
Today's GI pipe prices
Item | Wall | Price (THB) |
|---|---|---|
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 1/2 in | 1.8 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 1/2 in | 1.4 mm | |
GI Galvanized Steel Pipe Red Stripe Plain Ends 1/2 in | 1.4 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 3/4 in | 1.8 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 3/4 in | 1.4 mm | |
GI Galvanized Steel Pipe Red Stripe Plain Ends 3/4 in | 1.4 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 1 in | 1.8 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 1 in | 1.6 mm | |
GI Galvanized Steel Pipe Red Stripe Plain Ends 1 in | 1.4 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 1.25 in | 2 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 1.25 in | 1.6 mm | |
GI Galvanized Steel Pipe Red Stripe Plain Ends 1.25 in | 1.4 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 1.5 in | 2 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 1.5 in | 1.7 mm | |
GI Galvanized Steel Pipe Red Stripe Plain Ends 1.5 in | 1.4 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 2 in | 2 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 2 in | 1.7 mm | |
GI Galvanized Steel Pipe Red Stripe Plain Ends 2 in | 1.4 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 2.5 in | 2.3 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 2.5 in | 2 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 3 in | 2.5 mm | |
GI Galvanized Steel Pipe Yellow Stripe Class S Threaded Ends 3 in | 2.1 mm | |
GI Galvanized Steel Pipe Blue Stripe Class M Threaded Ends 4 in | 2.5 mm | |
GI Galvanized Steel Pipe Plain Ends 1.5 in (OD 48.6 mm) | 2.3 mm | |
GI Galvanized Steel Pipe Plain Ends 1.5 in | 3.2 mm | |
GI Galvanized Steel Pipe Plain Ends 2 in (OD 60.5 mm) | 2.3 mm | |
GI Galvanized Steel Pipe Plain Ends 2 in | 3.2 mm | |
GI Galvanized Steel Pipe Plain Ends 2.5 in | 3.2 mm | |
GI Galvanized Steel Pipe Plain Ends 3 in TIS 107-2566 | 2.3 mm | |
GI Galvanized Steel Pipe Plain Ends 3 in TIS 107-2566 | 3.2 mm | |
GI Galvanized Steel Pipe Plain Ends 4 in TIS 107-2566 | 2.3 mm | |
GI Galvanized Steel Pipe Plain Ends 4 in TIS 107-2566 | 3.2 mm | |
GI Galvanized Steel Pipe Plain Ends 6 in TIS 107-2566 | 2.5 mm | |
GI Galvanized Steel Pipe Plain Ends 6 in TIS 107-2566 | 3.2 mm |
Caring for GI pipe
Cut ends, welds and threads lose their zinc and rust first. Touch them up with zinc-rich or anti-rust paint after cutting or welding, and paint pipe that sits outdoors or near the sea.
Buy GI pipe at OneStockHome
Factory prices on every size and wall thickness, with delivery across Thailand. Not sure whether you need GI or HDG? Our team will check the spec with you before you order.
FAQ
Is GI pipe the same as galvanized steel pipe?
GI is one kind of galvanized steel pipe. The other is HDG, which has a thicker coating and is the one to use for water systems.
How long is a length of GI pipe?
6 meters for every size listed here.
Check today's price and order at OneStockHome with delivery across Thailand.
