2
edits
Changes
Added information on need to keep superstructure dark and origins of design.
The mesh size of the fly screen must be large enough to prevent clogging with dust and allow air to circulate freely. Aluminum screens, with a hole-size of 1.2 to 1.5mm have proven to be the most effective.
Care during superstructure design must be taken to ensure that flies inside the pit are not unduly attracted to light through the defecation hole either through utilization of small windows in the superstructure or provision of a removable cover for the defectation hole.
The top diameter of the Single VIP should be between 1 to 1.5mand be dug at least 3mdeep, although the deeper the better. Deep pits can last up to 15, 20, 30 or more years. As the effluent leaches from the Single VIP and migrates through unsaturated soils, faecal organisms are removed. The degree of faecal organism removal varies with soil type, distance traveled, moisture and other environmental factors and thus, it is difficult to estimate the necessary distance between a pit and a water source. A minimum distance of 30m between the pit and a water source is recommended to limit exposure to chemical and biological contamination.
To keep the Single VIP free of flies and odours, regular cleaning and maintenance is required. Dead flies, spider webs, dust and other debris should be removed from the ventilation screen to ensure a good flow of air.
==Origins==
The VIP latrine was developed in the 1970s at the Blair Research Laboratory in Zimbabwe.
==Acknowledgements==