Single Ventilated Improved Pit (VIP)

The single VIP is a ventilated improved pit. It is an improvement over the single pit because continuous airflow through the ventilation pipe vents odours and acts as a trap for flies as they escape towards the light.

Despite their simplicity, well-designed single VIPs can be completely smell free, and more pleasant to use than some other water-based technologies.

Flies that hatch in the pit are attracted to the light at the top of the ventilation pipe. When they fly towards the light and try to escape, they are trapped by the fly-screen and die. The ventilation also allows odours to escape and minimizes the attraction for flies.

Design Considerations

The vent pipe should have an internal diameter of at least 110 mm and reach more than 300 mm above the highest point of the toilet superstructure. Wind passing over the top creates a suction pressure within the vent pipe and induces an air circulation. Air is drawn through the user interface into the pit, moves up inside the vent pipe and escapes into the atmosphere. Care should be taken that objects, such as trees or houses, do not interfere with the air stream. The vent works best in windy areas, but where there is little wind, its effectiveness can be improved by painting the pipe black. The heat difference between the pit (cool) and the vent (warm) creates an updraft that pulls the air and odours up and out of the pit. To test the efficacy of the ventilation, a lit cigarette can be held over the user interface; the smoke should be pulled down into the pit and up into the vent and not remain in the superstructure.

The mesh size of the fly screen must be large enough to prevent clogging with dust and allow air to circulate freely. Aluminium screens, with a hole-size of 1.2 to 1.5 mm, have proven to be the most effective. Typically, the pit is at least 3 m deep and 1 to 1.5 m in diameter, depending on the number of users. Deep pits can last up to 20 or more years.

As liquid leaches from the pit and migrates through the unsaturated soil matrix, pathogenic germs are sorbed to the soil surface. In this way, pathogens can be removed prior to contact with groundwater. The degree of removal varies with soil type, distance travelled, moisture and other environmental factors and, thus, it is difficult to estimate the distance necessary between a pit and a water source. A minimum horizontal distance of 30 m between a pit and a water source and 2 m between the bottom of the pit and the groundwater table is normally recommended to limit exposure to microbial contamination.

When it is not possible to dig a deep pit or the groundwater level is too high, a raised pit can be a viable alternative: the shallow pit can be extended by building the pit upwards with the use of concrete rings or blocks. A raised pit can also be constructed in an area where flooding is frequent in order to keep water from flowing into the pit during heavy rain.

A single VIP toilet can be upgraded to a double VIP. A double VIP has an extra pit so that while one is in use, the contents of the full pit are allowed to drain, mature and degrade.

If a urine-diverting user interface is used, only faeces are collected in the pit and leaching can be minimized.

Appropriateness

Treatment processes in the single VIP (aerobic, anaerobic, dehydration, composting, or otherwise) are limited, and, therefore, pathogen reduction and organic degradation is not significant. However, since the excreta are contained, pathogen transmission to the user is limited. This technology is a significant improvement over single pits or open defecation.

Single VIPs are appropriate for rural and peri-urban areas; in densely populated areas they are often difficult to empty and/or have insufficient space for infiltration. VIPs are especially appropriate when water is scarce and where there is a low groundwater table. They should be located in an area with a good breeze to ensure effective ventilation. They are not suited for rocky or compacted soils (that are difficult to dig) or for areas that flood frequently.

Health Aspects/Acceptance

A single VIP can be a very clean, comfortable, and well accepted sanitation option. However, some health concerns exist:

  • Leachate can contaminate groundwater;
  • Pits are susceptible to failure and/or overflowing during floods;
  • Health risks from flies are not completely removed by ventilation.

Operation & Maintenance

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.

References

Further Readings

  • Cover image of a reference book or miscellany.

    TILLEY, E.; ULRICH, L.; LUETHI, C.; REYMOND, P.; SCHERTENLEIB, R.; ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies (Arabic). 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag). PDF

    This is the Arabic version of the Compendium of Sanitation Systems and Technologies. The Compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

  • Cover image of a reference book or miscellany.

    ARGOSS (Editor) (2001): Guidelines for Assessing the Risk to Groundwater from On-Site Sanitation. Keyworth: British Geological Survey. URL [Accessed: 30.09.2013]. PDF

    Many people in developing countries rely upon untreated groundwater supplies for their drinking water (e.g. from drilled boreholes, tube wells, dug wells or springs). The introduction of on-site sanitation systems might lead to groundwater contamination. The purpose of this manual is to provide guidance on how to assess and reduce the risk of contamination of groundwater supplies from on-site sanitation systems and is aimed at those responsible for planning low cost water supply and sanitation schemes.

  • Cover image of a reference book or miscellany.

    ECOSAN CLUB (Editor) (2012): Faecal Sludge Management.. Vienna: Ecosan Club. URL [Accessed: 16.10.2012]. PDF

    This issue presents studies from different regions (Bangladesh, Cameroon, Burkina Faso) that mainly show the non-existence of faecal sludge management. Additionally, the last paper describes a new technological solution (LaDePa) for producing hygienically safe organic fertiliser from sludge from ventilated improved pit toilets (VIPs).

  • Cover image of a reference book or miscellany.

    HARVEY, P.; BAGHRI, S.; REED, B. (2002): Emergency Sanitation: Assessment and Programme Design. Loughborough: Water, Engineering and Development Centre (WEDC). URL [Accessed: 21.02.2011]. PDF

    This book has been written to help all those involved in planning and implementing emergency sanitation programmes. The main focus is a systematic and structured approach to assessment and programme design. There is a strong emphasis on socio-cultural issues and community participation throughout.Includes an extensive “guidelines” section with rapid assessment instructions and details on programme design, planning and implementation.

  • Cover image of a reference book or miscellany.

    MARA, D.D. (1984): The design of Ventilated Improved Pit Latrines. UNDP Interregional Project. Washington: The World Bank. URL [Accessed: 11.10.2013]. PDF

    The purpose of this paper is to discuss general design criteria for VIP latrines and to review recent developments in VIP latrine design.

  • Cover image of a reference book or miscellany.

    MONVOIS, J.; GABERT, J.; FRENOUX, C.; GUILLAUME, M. (2010): How to Select Appropriate Technical Solutions for Sanitation. Cotonou and Paris: Partenariat pour le Développement Municipal (PDM) and Programme Solidarité Eau (pS-Eau). URL [Accessed: 19.10.2011]. PDF

    The purpose of this guide is to assist local contracting authorities and their partners in identifying those sanitation technologies best suited to the different contexts that exist within their town. The first part of the guide contains a planning process and a set of criteria to be completed; these assist you in characterizing each area of intervention so that you are then in a position to identify the most appropriate technical solutions. The second part of the guide consists of technical factsheets which give a practical overview of the technical and economic characteristics, the operating principle and the pros and cons of the 29 sanitation technology options most commonly used in sub-Saharan Africa.

  • Cover image of a reference book or miscellany.

    MORGAN, P.; EcoSanRes (Editor) (2009): Ecological Toilets. (pdf presentation). Stockholm: Stockholm Environment Institute. PDF

    This book describes how to construct Arborloo toilets and how it can be upgraded to VIPs at a later stage.

  • Cover image of a reference journal article.

    NATURE (Editor); MORGAN, P.; OTTERPOHL, R.; PARAMASIVAN, S.; HARRINGTON, E. (2012): Ecodesign: The Bottom Line. In: Nature: International Weekly Journal of Science 486, 186.URL [Accessed: 19.06.2012]. PDF

    There is no single design solution to sanitation. But there are universal principles for systematically and safely detoxifying human excreta, without contaminating, wasting or even using water. Ecological sanitation design — which is focused on sustainability through reuse and recycling — offers workable solutions that are gaining footholds around the world, as Nature explores on the following pages through the work of Peter Morgan in Zimbabwe, Ralf Otterpohl and his team in Germany, Shunmuga Paramasivan in India, and Ed Harrington and his colleagues in California.

  • Cover image of a reference book or miscellany.

    USAID Afghanistan (Editor) (2010): Latrine and Sanitation Options Manual. Sustainable Water Supply and Sanitation (SWSS) Project. Kabul: USAID Afghanistan. URL [Accessed: 15.01.2013]. PDF

    This Manual aims to serve as a practical guide for the selection of sanitation technology options to satisfy local desires and meet national needs in Afghanistan. It is useful for the professionals and organisations working to address fecal contamination across Afghanistan.

  • Cover image of a reference book or miscellany.

    RYAN, B.A.; MARA, D.D. (1983): Ventilated Improved Pit Latrines: Vent Pipe Design Guidelines. Washington: The World Bank, United Nations Development Programme (UNDP). URL [Accessed: 31.01.2014]. PDF

    This technical note sets out preliminary guidelines for the design and construction of vent pipes for ventilated improved pit (VIP) latrines.