- Manual removal of humus is required<br> - Possible contamination of groundwater<br> - Higher capital cost than Single VIP; reduced operating costs if self-emptied.
}}
[[Image:waterless pit system.png|none|1000px|]]
===Appropriateness===
<br>
===References===
* ARGOSS (2001). Guidelines for Assessing the Risk to Groundwater from on-Site Sanitation. British Geological Survey Commissioned Report, CR/01/142, Keyworth, UK. :Available at: [http://www.bgs.ac.ukbgs.ac.uk]
* Franceys, R., Pickford, J. and Reed, R. (1992). A Guide to the Development of on-Site Sanitation. WHO, Geneva, CH.
:Available at: [http://www.susana.org/librarysusana.org/library] * Graham, J. P. and Polizzotto, M. L. (2013). Pit Latrines and Their Impacts on Groundwater Quality: A Systematic Review.Environmental Health Perspectives, National Institute of Environmental Health Sciences, Research Triangle Park, US.:Available at: [http://www.ehponline.orgehponline.org] * Mara, D. D. (1984). The Design of Ventilated Improved Pit Latrines. UNDP Interregional Project INT/81/047, The World Bank and UNDP, Washington, D.C., US. :Available at: [http://documents.worldbank.org/curated/en/home documents.worldbank.org/curated/en/home ] (A good reference for detailed double VIP design information)
* Mara, D. D. (1996). Low-Cost Urban Sanitation. Wiley, Chichester, UK. (General description of VIPs with a focus on the ventilation system)
* Morgan, P. R. (2009). Ecological Toilets. Start Simple and Upgrade from Arborloo to VIP. Stockholm Environment
Institute, Stockholm, SE. :Available at: [http://www.ecosanres.orgecosanres.org]
===Acknowledgements===
{{:Acknowledgements Sanitation}}
