---
title: "Short note: WI and concrete pipe"
subject: "Water Supply Engineering"
chapter: 8
key: "semester_5/water_supply_engineering:wi-concrete-pipe-note"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/wi-concrete-pipe-note
site: BCT Engineering
---

# Short note: WI and concrete pipe

Water Supply Engineering · Chapter 8: Conveyance of Water

- Asked in: 2066 Jestha (old course)
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/wi-concrete-pipe-note
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-8

## Question

Write a short note on WI and concrete pipe.

## Short answer

Wrought iron pipe is lighter, stronger in tension, and can be threaded, but corrodes easily and is costlier. Concrete pipes (plain, RCC, or prestressed) are cheap for large diameters, have long life, and resist corrosion, but are heavy, crack under tension, and are attacked by acids; they are used for gravity mains and sewers.

## Answer

#### Wrought iron (WI) pipe
Wrought iron pipe is made from rolled and welded wrought iron plate.
- **Merits:** lighter than CI, stronger in tension, can be cut and threaded easily, and withstands shocks and vibration.
- **Demerits:** costlier than CI; corrodes (rusts) easily unless galvanised or coated, so its life is shorter; it has now been replaced by galvanised steel pipe. It is joined by screwed joints.

#### Concrete pipe
Concrete pipes are plain (up to 600 mm), reinforced (RCC) or prestressed.
- Made in a factory by spinning or casting; sizes 150 mm to over 3 m; joints are spigot-and-socket or collar with cement mortar or rubber rings.
- **Merits:** cheap for large diameters, long life (75 years), does not corrode, smooth after finishing, and can be made locally.
- **Demerits:** heavy and difficult to transport; may crack under tension and leak at joints; attacked by acids, sulphates; cannot withstand high pressure (plain/RCC up to about 30–60 m head; prestressed higher).
- Used for large gravity mains and sewers.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is the main drawback of wrought iron pipe?
   A. Weaker than CI in tension
   B. Brittle
   C. Rusts easily unless galvanised or coated
   D. Cannot be threaded
   Answer: C. WI corrodes easily, giving shorter life; replaced by galvanised steel. (Key point: WI demerit)

2. Why is WI better than CI in some respects?
   A. Does not corrode
   B. Lighter, stronger in tension, withstands shock and vibration
   C. Cannot be cut
   D. Heavier and more durable
   Answer: B. WI is lighter and tougher than brittle CI. (Key point: WI merit)

3. Where are concrete pipes mainly used?
   A. Exposed stream crossings
   B. High-pressure pumping mains
   C. Large gravity mains and sewers
   D. House connections
   Answer: C. They are cheap in large diameters but low-pressure. (Key point: Concrete use)

4. Why can plain/RCC concrete pipes not serve high-pressure lines?
   A. They are only 150 mm in size
   B. They crack under tension and leak at joints; limited to about 30-60 m head
   C. They corrode quickly
   D. They are too light
   Answer: B. Concrete is weak in tension, so pressure is limited unless prestressed. (Key point: Concrete limits)

## Related in Water Supply Engineering

- [Pipe requirements; concrete, CI, PPR pipes](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Apipe-requirements-concrete-ci-ppr) — Water Supply Engineering, chapter 8

## Related in other subjects

- [RCC slab culvert: brick, wearing coat, GI pipe, steel](https://www.bctengineer.com/question.md?key=semester_7%2Festimating_and_costing%3Aslab-culvert-a-fig-b) — Estimating and Costing, chapter 6