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Short note: GI and CI pipe

Short answer

GI pipe is galvanized steel, strong, cheap, used for house connections, joined by threaded sockets; it corrodes over time and life is 15–30 years. CI pipe is cast iron, very durable (100 years), corrosion-resistant, heavy, brittle, socket-spigot joints, prone to tuberculation unless lined.

Write a short note on GI and CI pipe.

Galvanised iron (GI) pipe

GI pipe is a steel pipe coated with a layer of zinc (galvanised) to protect it from rust.

  • Available in sizes 15–150 mm in 6 m lengths in three classes (light, medium, heavy).
  • Jointed by threaded sockets, unions, bends and tees (screwed joints).
  • Merits: strong, rigid and cheap; can take high pressure; easy to cut and thread; good for exposed lines, house connections and stream crossings.
  • Demerits: corrodes and scales (zinc is lost), especially in acidic or soft water, so the flow and the life (15–30 years) are reduced; heavy; limited to small sizes.

Cast iron (CI) pipe

CI pipe is cast from grey iron in lengths of 3–6 m with a socket at one end.

  • Used for distribution mains of 80 mm and larger.
  • Jointed by socket-spigot (lead and yarn), flanged or mechanical joints.
  • Merits: very long life (100 years), resists corrosion (better than steel), stands high pressures and external loads, easy to cut and tap.
  • Demerits: heavy, brittle (breaks under shock or uneven settlement), costly, and the interior roughens with tuberculation unless cement-mortar lined.

✓ Answer checked by Claude Opus 5.5 (high effort)

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