---
title: "Pipe joints; collar joint"
subject: "Water Supply Engineering"
chapter: 8
key: "semester_5/water_supply_engineering:pipe-joints-collar"
source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/pipe-joints-collar
site: BCT Engineering
---

# Pipe joints; collar joint

Water Supply Engineering · Chapter 8: Conveyance of Water

- Asked in: 2079 Baisakh, 1+2 marks
- Video: [Types of Pipe Joints in Environmental Engineering 🔥🔥🔥🔥](https://www.youtube.com/watch?v=Ipmmtwz4uuA) — Civil Notebook
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/pipe-joints-collar
- Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-8

## Question

Why are pipe joints required? Describe the collar joint with a neat sketch.

## Short answer

Pipes are joined to form a continuous watertight line. A collar joint uses a short sleeve slipped over plain pipe ends; the annular gap is sealed with cement mortar, yarn, lead, or a rubber ring. It is simple, cheap, and watertight but rigid and unsuitable for high pressure.

## Answer

#### Why pipe joints are required
Pipes come in short lengths (3–6 m) and must be joined to make a long, watertight line, and to connect fittings such as valves and bends.

#### Collar joint
A collar joint is used for plain-ended pipes, such as concrete, asbestos cement, or CI pipes without sockets. A short pipe-like sleeve, called a **collar** (with an inside diameter slightly more than the pipe), is slipped over the ends of the two pipes. The pipes are placed with a small gap in the middle, and the annular space on both sides is filled with cement mortar (1 : 1), yarn and lead or a rubber ring.

```text
          collar
       ___________
  =====|=========|=====  pipe ends meet in the middle
       |_________|       gaps sealed with mortar,
     pipe 1  gap  pipe 2    yarn or rubber ring
```
It is simple, cheap and watertight, but rigid and not suited to high pressure.

## Check yourself

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

1. Why are pipe joints required?
   A. Pipes are short (3-6 m) and must form a long watertight line
   B. To change the water colour
   C. To increase pipe strength
   D. To reduce flow
   Answer: A. Short lengths must be joined and connected to fittings. (Key point: Need for joints)

2. For which pipes is a collar joint used?
   A. Only threaded GI
   B. Only socketed CI
   C. Plain-ended pipes such as concrete or asbestos cement
   D. Only PVC with solvent
   Answer: C. Plain-ended pipes have no socket, so a collar sleeve is used. (Key point: Collar use)

3. How is the collar joint made watertight?
   A. Annular space is filled with cement mortar, yarn and lead or rubber ring
   B. Pipes touch fully and are welded
   C. Collar is screwed on
   D. Gasket and bolts
   Answer: A. The collar is slipped over two pipe ends with a small gap and the annulus sealed. (Key point: Collar working)

4. What is a drawback of the collar joint?
   A. Not watertight
   B. Needs a fusion machine
   C. Rigid and not suited to high pressure
   D. Expensive and complicated
   Answer: C. It is simple and cheap but rigid. (Key point: Collar limits)

## Related in Water Supply Engineering

- [Pipe joints; socket and spigot joint](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Apipe-joints-socket-spigot) — Water Supply Engineering, chapter 8, asked 4×
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