Double Ventilated Improved Pit (VIP)

The double VIP has almost the same design as the single VIP with the added advantage of a second pit that allows it to be used continuously and permits safer and easier emptying.

By using two pits, one pit can be used, while the content of the second rests, drains, reduces in volume, and degrades. When the second pit is almost full (the excreta is 50 cm from the top of the pit), it is covered, and the content of the first pit is removed. Due to the extended resting time (at least 1 or 2 years after several years of filling), the material within the pit is partially sanitized and humus-like.

Design Considerations

The superstructure may either extend over both holes or it may be designed to move from one pit to the other. In either case, the pit that is not being filled should be fully covered and sealed to prevent water, garbage and animals, or people from falling into the pit. The ventilation of the two pits can be accomplished using one ventilation pipe moved back and forth between the pits, or each pit can be equipped with its own dedicated pipe. The two pits in the double VIP are continually used and should be well lined and supported to ensure longevity.

Appropriateness

The double VIP is more appropriate than the single VIP for denser, peri-urban areas. After the resting time, the soil-like material is manually emptied (it is dug out, not pumped out), so vacuum truck access to the pits is not necessary.

The double VIP technology will only work properly if the two pits are used sequentially and not concurrently. Therefore, an adequate cover for the out of service pit is required. Double 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 allow for proper ventilation. They are not suited for rocky or compacted soils (that are difficult to dig) or for areas that flood frequently.

Health Aspects/Acceptance

The double VIP can be a very clean, comfortable and well accepted sanitation option, in some cases even more so than a water-based technology. 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 double 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. The out of service pit should be well sealed to reduce water infiltration and a proper alternating schedule must be maintained.


References

Further Readings

  • 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.

    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.

    WATERAID (2008): Technology Notes. London: WaterAid. URL [Accessed: 04.01.2011]. PDF

    These technology notes have been prepared following many general enquiries for technical information having been received by WaterAid over the years. Their purpose is to give an outline of the technologies used by WaterAid on long-term development projects in Africa and Asia, and to show alternatives, which might be appropriate in different circumstances. It may be possible to determine from the notes the technology, which would be appropriate in a particular location.

Case Studies

  • Cover image of a reference book or miscellany.

    LUETHI, C.; NIWAGABA, B.C.; GUENTHER, I.; HORST, A.; MULONGO, P.; GRUETER, R. (2013): Ventilated Improved Latrine Construction in the Slum Areas of Kampala, Uganda. Technical Factsheet. Zuerich: Nachdiplomstudium fuer Entwicklungslaender (NADEL) Eidgenoessische Technische Hochschule (ETH). URL [Accessed: 10.10.2013]. PDF

    The Urban Affordable Clean Toilets (U-ACT) project aims at overcoming the constraints to private sanitation investment in poor urban areas. Field research was conducted in 40 randomly selected low-income areas of Uganda’s capital Kampala where people rely on on-site sanitation. The sanitation situation in these urban slum zones is characterised by a high number of users per toilet, and full or overflowing latrines that are not regularly emptied. This factsheet provides information on the construction and cost details of ventilated improved pit (VIP) latrines.