Galvanised iron (GI) pipe was the standard water pipe in older Lahore houses. Many new homes now use PPR or UPVC for concealed supply, but GI is still bought for exposed lines, roof and boundary work, pump connections, structural uses like railings and sheds, and repair work on older buildings.
Types and specifications
| Item | What it is | Used for |
|---|---|---|
| GI pipe | Steel pipe with zinc coating inside and out, threaded ends | Exposed water lines, pump and tank connections, boring, mechanical work |
| Wall-thickness classes | Lighter and heavier wall versions of the same nominal size | Heavier walls for pressure, burial or structural use |
| GI fittings | Malleable iron elbows, tees, sockets, unions, nipples, reducers | Threaded joints |
| Black (ungalvanised) pipe | Same steel pipe without zinc | Structural and fabrication work, not drinking water |
| Thread sealant, tape and hemp | Jointing materials | Sealing threaded joints |
GI is sold by nominal bore (diameter) and wall class. Ask the supplier which standard and class each pipe is made to, and check that it is printed or stencilled on the pipe.
What each is used for
- Exposed supply lines on roofs and outer walls where impact resistance matters
- Pump suction and delivery connections
- Borewell and hand pump columns
- Railings, grills, frames and sheds (often black or GI pipe)
- Repairs to existing GI systems in older houses
For concealed indoor supply in a new house, discuss with your plumber whether PPR is a better choice, since GI can corrode inside over time.
Quality checks on delivery
- Markings: size, class and maker's marking on each pipe.
- Wall thickness: check at the cut end with a caliper or compare against a known pipe of the same class.
- Weight: a noticeably lighter pipe of the same size and class may have a thinner wall. Weigh a sample length if quantities are large.
- Galvanising: even, bright or grey zinc coating, inside and out. No bare patches, flaking or rust.
- Threads: clean, complete, undamaged, with protective caps or sockets on ends.
- Straightness: no bends or dents.
- Fittings: threads matching the pipe, no casting cracks.
- Count: check every line of the invoice.
How much you need
There is no reliable per-square-foot rule for GI. Ask your plumber for a take-off listing pipe sizes and lengths and each fitting. For structural uses, your fabricator or engineer will give lengths by size and class.
Bulk-buying tips
- Confirm how it is sold: by length (piece) or by weight. If by weight, ask for a weighbridge or scale slip.
- Invoice detail: size, class, quantity and rate on each line.
- Delivery: long, heavy lengths need a suitable vehicle and enough people for safe unloading.
- Payment: pay after checking, or stage payments if deliveries are split.
- Storage: keep off the ground on wooden supports, under cover, away from standing water to protect the zinc coating.
- Cutting and threading: re-threaded ends lose galvanising; protect them with a suitable coating.
What affects the price
- Nominal size and wall class
- Galvanised versus black pipe
- Market steel and zinc prices
- Priced per length or per weight
- Quantity and full bundles
- Fittings mix
- Delivery distance
We do not publish rates. Get written quotes on the same list, and ask whether rates are per length or per kilogram.
FAQs
Is GI pipe still used in new houses? Less for concealed water supply, more for exposed, pump, boring and structural work.
Why does old GI pipe give rusty water? Over many years the zinc layer wears and the steel corrodes inside, reducing flow and discolouring water.
How do I know if a GI pipe is underweight? Compare wall thickness and weigh a sample against the class and size stated on the invoice.
Can I join GI to PPR? Yes, using threaded brass-insert PPR fittings or adaptors. Your plumber will choose the right fitting.
Should GI pipe be painted? Exposed GI on roofs and walls lasts longer with a protective paint, especially at re-threaded ends.
Sources
No external figures or standards are cited on this page. Ask suppliers which standard and class each pipe is made to, and get it on the invoice.