GI pipe 4 inch is hot-dip galvanized steel pipe in the 4 inch nominal size, with an outside diameter of about 114.3 mm. This size suits bulk water mains, fire service mains and pump station pipework.
The zinc coating protects the steel inside and out. In addition, the pipe takes standard 4 inch GI fittings, so elbows, tees and sockets of the same size screw straight on.
What is GI pipe 4 inch?
GI pipe is steel pipe that has been hot-dip galvanized, meaning it was dipped in molten zinc. The zinc bonds to the steel and corrodes first, so the pipe resists rust much longer than bare steel.
GI pipe is sized by nominal bore in inches and made in light, medium and heavy wall grades. In Kenya these are often called Class A, Class B and Class C. Threaded ends join with GI fittings, while larger sizes may use flanges or couplings.
Further reading
- How hot-dip galvanization protects steel (Wikipedia)
- Nominal pipe size and outside diameter (Wikipedia)
- Pipes for carrying fluids: materials and uses (Wikipedia)
Key terms explained
- Galvanized iron (GI)
- Iron or steel coated with a layer of zinc. The zinc corrodes first, so it protects the metal underneath from rust.
- BSP thread
- British Standard Pipe thread, the common pipe thread in Kenya. Tapered BSP threads (BSPT, ISO 7-1) tighten into a seal as you screw them together.
- Nominal size
- The trade size of a pipe or fitting, such as 1/2 inch. It names the pipe size, so it is not an exact measurement of the outside diameter.
- Thread sealant
- PTFE tape, hemp with jointing paste, or an anaerobic sealant applied to male threads. It fills tiny gaps so the joint does not leak.
- Outside diameter (OD)
- The measured width across the outside of the pipe. Pipes of the same nominal size share the same OD, whatever the wall grade.
- Class A, B and C
- Local names for light, medium and heavy wall GI pipe. A thicker wall handles more pressure and abuse.
Features and benefits
- Hot-dip zinc coating on the inside and outside surfaces.
- Strong steel wall that resists knocks, crushing and sunlight.
- Takes standard BSP threads and GI fittings.
- Rigid, so it needs fewer supports than plastic pipe.
- Light and medium wall grades for different pressures.
- Sizes from 1/2 inch to large mains.
Technical specifications
| Product | GI Pipe 4 Inch |
|---|---|
| Nominal size | 4" |
| Outside diameter | 114.3 mm |
| Material | Hot-dip galvanized steel |
| Wall grade | Light (Class A) or medium (Class B), confirm with quote |
| Ends | Threaded or plain, confirm with quote |
| Matching fittings | 4 inch GI fittings, female BSP |
| Supplier | Sparks Plumbing Experts Ltd, Nairobi |
Wall thickness, length per piece and end finish depend on the grade and batch. Tell us the grade and quantity, and we will confirm current stock.
Applications of GI pipe 4 inch
- Domestic water supply. Carries mains water into homes, flats and offices.
- Rising mains. Feeds water up through multi-storey buildings.
- Borehole riser pipes. Lifts water from submersible pumps to the surface.
- Rooftop tank lines. Connects elevated tanks to building supply lines.
- Farm irrigation mains. Carries water above ground across farms and greenhouses.
- Fire hose reel and hydrant feeds. Supplies water to hose reels and hydrants where GI is specified.
- Pump station pipework. Forms suction and delivery lines around water pumps.
- Industrial process water. Carries cooling and wash water in factories and workshops.
- Livestock water lines. Supplies troughs and dips on farms and ranches.
- Outdoor standpipes. Forms exposed standpipes and yard taps that must resist knocks.
- Cable and pipe sleeves. Protects cables or plastic pipes where they pass through walls or under driveways.
- Fencing and gates. Serves as posts, rails and gate frames on homes and farms.
- Handrails and balustrades. Forms rust-resistant rails on stairs, ramps and walkways.
- Greenhouse and shade frames. Builds the frames for greenhouses, shade nets and carports.
- Tank stands and supports. Makes light supports and brackets for tanks and equipment.
How to choose and install
- Size the pipe from the flow you need and the length of the run, or ask your engineer.
- Choose the wall grade (Class A or B) to suit the pressure, burial and exposure.
- Order matching GI fittings of the same nominal size.
- Paint or wrap pipe that will be buried in aggressive soil, because zinc wears faster underground.
- Avoid direct contact with copper. Use a brass or dielectric transition instead.
- Flush new lines before use to clear cutting debris and loose zinc.
Why choose Sparks Plumbing Experts
- Every common pipe materialGI, PPR, PVC, HDPE, brass and stainless fittings are all stocked, so you can match any existing system.
- Common sizes in stockMost fitting types come in several sizes, from small domestic sizes up to larger mains sizes.
- Pipes, fittings and valves togetherPipes, fittings, valves, clamps and jointing products come in one order.
- Help with thread and size standardsWe help you confirm inch and millimetre sizes before you buy, which avoids return trips.
- Visit or collect in NairobiOur store is at KCB Building, Enterprise Road, in the Industrial Area, so you can see parts before you buy or collect your order.
- Quotes your wayAsk for prices by phone, WhatsApp, email or the online quote form, whichever suits you on site.
- Over 1,600 products in one placeOur catalogue covers 55 categories, so one supplier can handle most of your parts list.
- Help choosing the right partSend a nameplate photo, a drawing or the old part, and we help you match size and specification.
- Single items or project quantitiesWe price a single replacement part just as readily as a full site order.
- Supply across East AfricaWe serve customers across Kenya, and we also supply buyers in Uganda and Tanzania.
Related products and accessories
Browse more: GI Pipes & Fittings · Valves · Flanges · Tapes.
Ordering from Sparks Plumbing Experts
We supply customers across Kenya, and we also serve buyers in Uganda and Tanzania. You can collect from our store at KCB Building, Enterprise Road, Nairobi, or ask us about delivery to your site. Send your quantities and specifications, and we will reply with prices and availability.
Request a Quote WhatsApp 0726 086 895
Frequently asked questions
What is the outside diameter of GI pipe 4 inch?
About 114.3 mm. Measure an existing pipe with a tape or caliper to confirm the size before you order.
Which fittings fit GI pipe 4 inch?
4 inch GI fittings with female BSP threads, such as elbows, tees, sockets and unions.
Is this GI pipe 4 inch Class A or Class B?
This page covers 4 inch GI pipe in general. Tell us whether you need light (Class A) or medium (Class B) wall, and we will confirm stock.
Can I order GI pipe 4 inch in bulk?
Yes. We supply single lengths and bulk quantities for contractors. Include the number of lengths in your quote request.
What details do you need to quote GI pipes?
Tell us the size, the quantity and what the item will connect to. A photo of the old part or a drawing also helps. Then call or WhatsApp 0726 086 895, or use the quote form on this page.
Do you deliver GI pipes outside Nairobi?
Yes. We supply customers across Kenya, and we also serve buyers in Uganda and Tanzania. Delivery or courier arrangements are agreed when you confirm the order.
How much does a GI pipe cost in Kenya?
The price depends on the size, the quantity and current steel prices. Therefore, send your list with a quote request and we will reply with current figures.
Should I use PTFE tape or paste on GI pipes?
Either works when applied correctly. Wrap PTFE tape clockwise on the male thread, or use hemp with jointing paste on larger sizes. Do not over-tighten, because that can crack the fitting.
Can GI pipes connect to copper pipe?
Avoid a direct joint between galvanized steel and copper, because the zinc then corrodes quickly. Instead, use a brass adaptor or, better, a dielectric union as the transition.
Can GI pipe be buried?
Yes, but zinc wears faster in wet or acidic soil. Therefore, wrap or coat buried GI pipe, or consider HDPE for long buried runs.
Is GI pipe suitable for hot water?
Yes, for normal domestic hot water. However, zinc corrodes faster above about 60 degrees Celsius, so hot lines may need replacing sooner.
Can GI pipe carry drinking water?
Galvanized pipe has long carried cold water. However, many new drinking water systems use PPR or HDPE, so follow your project specification.
People also search for
GI pipe Class A vs Class B
Class A is the light wall grade and Class B the medium grade. Class B suits higher pressure and buried mains.
GI pipe vs PPR pipe
GI is stronger and handles sunlight and knocks. PPR does not rust and suits hot and cold water inside buildings.
GI pipe vs HDPE pipe
HDPE is flexible and corrosion free, so it suits buried mains. GI is rigid and suits exposed lines.
GI pipe sizes in mm
Common outside diameters: 1/2 inch about 21.3 mm, 1 inch about 33.7 mm, 2 inch about 60.3 mm, 4 inch about 114.3 mm.
GI pipe price in Kenya
Prices depend on size, grade and steel costs. Request a quote from Sparks Plumbing Experts for current figures.
how to thread GI pipe
Cut the pipe square, then use a pipe die stock with BSP dies and cutting oil. Clean the thread before sealing.
how long does GI pipe last
It often lasts decades above ground. However, aggressive water or soil shortens its life.
galvanized vs black steel pipe
Black steel has no zinc coat and suits gas and closed heating loops. Galvanized suits water.
BS 1387 and EN 10255
These standards cover threadable steel tubes in light, medium and heavy series. EN 10255 replaced BS 1387.
GI pipe weight per metre
Weight depends on size and wall grade. Ask us for the figure for the grade you plan to order.
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