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close this bookA Guide to the Development of on-site Sanitation (WHO; 1992; 246 pages)
View the documentPreface
open this folder and view contentsPart I. Foundations of sanitary practice
close this folderPart II. Detailed design, construction, operation and maintenance
open this folder and view contentsChapter 5. Technical factors affecting excreta disposal
close this folderChapter 6. Operation and maintenance of on-site sanitation
View the documentPit latrines
View the documentSimple pit latrines
View the documentVentilated pit latrines
View the documentVentilated double-pit latrines
View the documentPour-flush latrines
View the documentOffset pour-flush latrines
View the documentDouble-pit offset pour-flush latrines
View the documentRaised pit latrines
View the documentBorehole latrines
View the documentSeptic tanks
View the documentAqua-privies
View the documentDisposal of effluent from septic tanks and aqua-privies
View the documentComposting latrines
View the documentMultiple latrines
View the documentOther latrines
open this folder and view contentsChapter 7. Components and construction of latrines
open this folder and view contentsChapter. 8 Design examples
open this folder and view contentsPart III. Planning and development of on-site sanitation projects
View the documentReferences
View the documentSelected further reading
View the documentGlossary of terms used in this book
View the documentAnnex 1. Reuse of excreta
View the documentAnnex 2. Sullage
View the documentAnnex 3. Reviewers
View the documentSelected WHO publications of related interest
View the documentBack Cover


An aqua-privy is a latrine set above or adjacent to a septic tank and is useful in situations in which there is a limited water supply (Fig. 6.25). Where the latrine is above the tank, a chute drop-pipe, 100-150 mm in diameter, hangs below the squat hole or latrine seat so that excreta drops directly into the tank below water level. The bottom of the pipe should be 75 mm below the liquid level in the tank, providing a seal which prevents gases escaping into the latrine superstructure and limits the access of flies and mosquitos to the tank. Alternatively the toilet may be fitted with a pan with a water seal. Where the latrine is adjacent to the tank, the pan with water seal is connected by a short pipe. Effluent from the tank goes to a soakpit, drainage trench or sewer. There is usually only a small flow of effluent and it is therefore very concentrated.

Fig. 6.25. Aqua-privy


WHO 91444

In order to keep a seal at the bottom of the drop-pipe it is essential that the water level in the tank is maintained. If the tank is completely watertight, a bucketful of water every day, used to clean the latrine, is sufficient to compensate for any losses due to evaporation. However, it has been found in practice that many tanks leak. In some places sullage is discharged into the tank (Fig. 6.26), but even this has not proved sufficient to ensure that the water level is above the bottom of the drop-pipe at all times. In Calcutta, aqua-privies used by people who use water for anal cleaning have a water seal incorporated in the drop-pipe below the pan (Pacey, 1978).

Fig. 6.26. Aqua-privy with pan flushed by waste from a washing trough


WHO 91445

The design capacity of aqua-privy tanks may be calculated by the same procedure as for septic tanks. Regular removal of sludge and scum is essential, so a removable cover for desludging is required. A vent pipe is usually provided.

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