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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
 

Raised pit latrines

Another way of dealing with the problem of difficult ground conditions close to the surface is to construct raised pit latrines. The pit is excavated as deep as possible, working at the end of the dry season in areas of high groundwater. The lining is extended above ground level until the desired pit volume is achieved.

If the pit extends more than 1.5 m below the ground there will probably be sufficient leaching area below ground for a pit latrine having a full depth of 3.5 m. In such cases, the lining above ground should be sealed by plastering both sides (Fig. 6.17). The minimum below-ground depth depends on the amount of water used in the pit and the permeability of the soil. Where insufficient infiltration area can be obtained below ground level, the raised portion of the pit can be surrounded by a mound of soil. The section of the lining above ground (excluding the top 0.5 m) can be used for infiltration provided the mound is made of permeable soil, well compacted with a stable side slope, and is thick enough to prevent filtrate seeping out of the sides (Fig. 6.18). Earth mounds are not recommended on clay soils as the filtrate is likely to seep out at the base of the mound rather than infiltrate the ground.


Fig. 6.17 Raised pit latrine

 

WHO 91436


Fig. 6.18. Mound latrine

 

WHO 91437

Raised pits can be used in combination with any other type of pit latrine (VIP, pour-flush, double-pit). A common application is where the groundwater level is close to the surface. A slight raising of the pit may prevent splashing of the user or blockage of the pit inlet pipe by floating scum.

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