Latrines are vital for community health. They keep local water used for drinking or growing crops free from diseases spread through human feces; and they discourage transmission of diseases by flies that breed in excrement.
In many areas, community acceptance of latrines as an integral part of any home, school, or clinic project may be more important than any other construction ideas in this manual.
Basically, a latrine consists of: a pit dug in the ground for the storage of excrement; a base built over the nit with a small hole in it so that a person can stand over the pit; and a shelter to provide privacy, protect against weather, and to keep flies from breeding in the pit.
Two principal requirements should govern the choice of a latrine's location:
* It should be close enough to the school, clinic, or home to be reached easily; but far enough away to keep the main building free of odors and potential contamination. 30 meters is the distance recommended by many experts.
* It should be situated so that it will not contaminate ground or surface water that may enter springs, wells, or fields. Satisfying this requirement can sometimes be complex.
The most important considerations to keep in mind are:
• the latrine should be high enough so it will not be flooded during the rainy season;
• the latrine should be downhill from any nearby wells or springs; if this is impossible - of if the land is flat - the latrine must be at least 15 meters away from wells or springs (7.5 meters in sandy soil);
• in regions with fissured rocks or limestone foundations (which can carry pollution great distances), get expert advice!
At the chosen location, begin by digging a pit, either round or square, about 1 meter across, and from 1-3 meters deep. The table below shows recommended depths for a latrine for a family of 5. The same depths may be used for latrines in public buildings such as schools or clinics provided there will be 1 latrine for every 15 people who use the building regularly.
On the table, "wet pit type" refers to pits which penetrate the water table in the ground and are constantly wet. "Dry pit type" refers to pits that are 3 meters or more above the highest underground water level.
If the soil is soft and tends to cave in during the digging, line the pit with stone, brick, wood, or bamboo to keep the sides of the pit strong. Even when the soil is firm, it's a good idea to line the upper few feet.
The base is essentially a foundation for the floor. It also helps to prevent hookworm larvae and burrowing rodents from entering the pit.
The best materials for the base are concrete from a 1:2:3 mixture, or stabilized earth with 5-6% cement content. Heavy hewn logs treated for insect resistance may also be used as shown.
Following construction of the base, a mound of hard-packed earth or dry fill should be built up until it is level with the top of the base (at least 15cm above ground level), and it covers the floor area planned for the shelter.
Above this mound must be placed a floor with a built-in hole about 40cm long and 12-18cm wide. Do not make the hole wider than 18cm or children may fall through it!
The shape of the hole can vary according to local preference. Two common shapes are shown.
The floor may be built of several materials. Reinforced concrete is best. Build a form about 100cm x 100cm and 6cm deep. Then cut a piece of wood 6cm high and the size and shape of the hole desired. This piece will act as the mold for the hole in the concrete slab. If you slope its sides slightly instead of making them straight up and down, it will be easier to remove from the concrete after the concrete has set.
Place the wood piece inside the 100cm x 100cm form where you want the hole to be. Then place reinforcement rods (bamboo or iron) in a grid across the formwork.
Mix, pour and cure the concrete as you would for any concrete floor (see pages 154-156), After curing, place the concrete slab over the mound and base so that the hole is centered over the pit opening.
Other materials appropriate for building latrine floors include reinforced brick mortar, wood, and logs with earth.
It may be desirable to add raised foot rests, approximately 30cm long and 10cm wide as shown.
In addition, a simple wood cover can greatly reduce odors and keep flies away from the pit.
The latrine shelter serves several purposes:
• protection from wind and rain;
• protection of the pit from direct light (darkness keeps flies and other disease-carrying insects and rodents from breeding in the pit).
In general, the shelter should be about 1 meter wide, 1.5 meters long, and 1.5 meters high.
It should have a shed roof with a large overhang [about 60l00cm). The roof should be 10-15cm above the walls for ventilation to diffuse any odors which might build up.
If acceptable socially, it is beat to cut all vegetation within 2 meters of the shelter, especially if food is grown nearby. This will prevent contamination of the ground surface resulting from any possible misuse of the latrine.
The illustrations above show two types of latrine shelter. The actual construction of latrine shelters follows the normal procedures for any building.
One final note: The latrine design described in this manual is only one of the many possible designs. See the sources listed in the bibliography (page 227) for information on other designs.