Ventilated improved pit latrines: recent developments in Zimbabwe

ABSTRACT

This paper describes recent developments in Zimbabwe in the design of ventilated improved pit latrines (VIP). Two basic designs are presented; one suitable for peri-urban areas and the other; a low-cost version of the first; for rural areas. The peri-urban VIP latrine consists of a circular pit (1.5 m diameter; 3 m deep) fully or partially lined with cement mortar and with; at its top; a brick collar on which is supported a 1.9 m diameter; 75 mm thick concrete slab precast on site. A 1.8 m high spiral shaped superstructure in construct on the cover slab in ferrocement or brick and a flat roof slab placed on top. A 150 mm diameter asbestos cement or polyvinyl chloride vent pipe with a fly screen at its top is then erected immediately adjacent to the outside of the superstructure (alternatively a brick vent pipe may be used in conjuction with a brick superstructure). A commercial kit version of this design is also described. The rural VIP latrine consitsts of a rectangular pit (1.5 m x 0.6 m x 3 m) over which are placed longitudinal and transverse wooden logs of around 100 mm diameter which are then covered with anthill soil and a thin layer of cement mortar. A spiral superstructure is then built in mud and wattle; thatch; soil or local bricks and covered with a conically shaped thatched roof. The vent pipe is made from local reeds; fitted with a fly screen and rendered with cement mortar. Both the peri-urban and rural VIP latrine designs have been found to be socially acceptable in Zimbabwe (where some 20 000 have been built) and very effective in eliminating odors and controlling fly breeding in the latrine