Pit privy: purpose and construction

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.

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