---
title: "Pit privy: purpose and construction"
subject: "Sanitary Engineering"
chapter: 9
key: "semester_6/sanitary_engineering:pit-privy-purpose-construction"
source: https://www.bctengineer.com/q/semester_6/sanitary_engineering/pit-privy-purpose-construction
site: BCT Engineering
---

# Pit privy: purpose and construction

Sanitary Engineering · Chapter 9: Disposal of Sewage from Isolated Buildings

- Asked in: 2073 Magh, 4 marks
- Video: [Design criteria + Procedure of VIP or PIT lattrine l|5thsem|Sanitary Engineering|CTEVT|Prashant YT|](https://www.youtube.com/watch?v=pdrROcvvDlU) — Prashant YT
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/sanitary_engineering/pit-privy-purpose-construction
- Whole chapter: https://www.bctengineer.com/md/semester_6/sanitary_engineering/chapter-9

## Question

What is the purpose of pit privy? Describe the construction of pit privy with a neat sketch.

## Short answer

A pit privy isolates excreta, preventing faecal-oral diseases. It consists of a lined pit 1–1.2 m diameter, 2–3 m deep with open-jointed lining and watertight top 0.3 m, a slab with squat hole, a superstructure, and is sited ≥15 m from wells.

## Answer

#### Purpose

A **pit privy** (pit latrine) is the simplest on-site sanitation facility, used where there is no sewerage or water supply for flushing. Its purpose is to collect and store human excreta in a pit so that they are isolated from people, flies and water sources, while the excreta decompose in the pit and the liquid soaks into the soil. It prevents open defecation and the spread of faecal-oral diseases (diarrhoea, cholera, typhoid, worms).

#### Construction

1. **Pit:** dug 1.0-1.2 m in diameter (or square) and 2-3 m deep (size from 0.06 m³/person/year); lined with open-jointed brick/stone, bamboo or wood to prevent collapse; the top 0.3 m is lined watertight and raised above ground to keep out surface water.
2. **Slab:** an RCC, wood or stone slab (about 1.2 m $\times$ 1.2 m) over the pit, with a squat hole of 0.2-0.25 m diameter and a cover lid.
3. **Superstructure:** about 1.0 m $\times$ 1.2 m in plan and 2 m high, with walls of brick, bamboo or corrugated sheet, a light roof and a door.
4. **Location:** at least 15 m from a well/spring and 6 m from a house, and downstream of water sources; the pit bottom at least 1.5 m above the ground-water level.
5. When the pit fills to 0.5 m below the slab, it is covered with soil and a new pit is dug.

```text
    ______________
   | superstructure|
   |___ O (hole)___|__ slab, 1.2 x 1.2
 ##|               |##  <- raised collar
   |  pit 2-3 m    |
   | (lined,       |
   |  open joints) |
   |_______________|
```

## Check yourself

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

1. What is the main purpose of a pit privy?
   A. Treat sewage for reuse
   B. Supply flushing water
   C. Collect rainwater
   D. Store excreta in a pit isolated from people, flies and water
   Answer: D. It isolates excreta so diseases are not spread; liquid soaks in. (Key point: Purpose)

2. Why is the top 0.3 m of the pit lined watertight and raised?
   A. Keep out surface water
   B. Hold the slab weight only
   C. Reduce odour only
   D. Allow flushing
   Answer: A. A raised watertight collar prevents surface runoff entering the pit. (Key point: Pit lining)

3. Minimum distance from a well or spring?
   A. 3 m
   B. 15 m
   C. 6 m
   D. 50 m
   Answer: B. At least 15 m from a water source; 6 m is from the house. (Key point: Location)

4. What is done when the pit is filled to 0.5 m from the slab?
   A. Empty with a bucket
   B. Add water
   C. Cover with soil and dig a new pit
   D. Raise the slab
   Answer: C. The pit is closed with soil and a new one dug. (Key point: When full)

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