The simple pit latrine (Fig. 6.3) consists of a hole in the ground (which may be wholly or partially lined) covered by a squatting slab or seat where the user defecates. The defecation hole may be provided with a cover or plug to prevent the entrance of flies or egress of odour while the pit is not being used.
The cover slab is commonly surrounded by some form of superstructure that provides shelter and privacy for the user. The superstructure design is irrelevant to the operation of the latrine but crucial to the acceptability of the latrine to the user. Superstructures range from a simple shelter of sacks or sticks to a building of bricks or blocks costing more than the rest of the latrine. The choice of superstructure will reflect the income and customs of the user.
Fig. 6.3. Simple pit latrine
The cover slab should be raised at least 150 mm above the surrounding ground to divert surface water away from the pit. Commonly, the cover slab sits directly on the lining, but if the lining is made of very thin material, such as an old oil drum, a concrete foundation beam may be necessary to distribute the load of the slab to the lining and surrounding ground (Fig. 6.4).
Fig. 6.4. Ring beam on top of a thin pit lining to support the cover slab
The simple pit latrine is the cheapest form of sanitation possible. Once constructed it requires very little attention other than keeping the latrine area clean and ensuring that the hole cover is in place when the latrine is not in use. Unfortunately the superstructure frequently becomes infested with flies and mosquitos and full of pungent odours because users do not replace the squat hole cover after use. Self-closing hole covers have been tried but are often disliked because the cover rests against the user's back. There may also be resistance to constructing new simple pit latrines because of their resemblance to existing, badly constructed, pit latrines.