Urine-Diverting Dry Toilet (UDDT)

A urine-diverting dry toilet (UDDT) is a toilet that operates without water and has a divider so that the user, with little effort, can divert the urine away from the faeces.

The UDDT is built such that urine is collected and drained from the front area of the toilet, while faeces fall through a large chute (hole) in the back. Depending on the Collection and Storage/Treatment technology that follows, drying material such as lime, ash or earth should be added into the same hole after defecating.


Design Considerations

It is important that the two sections of the toilet are well separated to ensure that a) faeces do not fall into and clog the urine collection area in the front, and that b) urine does not splash down into the dry area of the toilet. There are also 3-hole separating toilets that allow anal cleansing water to go into a third, dedicated basin separate from the urine drain and faeces collection. Both a pedestal and a squat slab can be used to separate urine from faeces depending on user preference.

Urine tends to rust most metals; therefore, metals should be avoided in the construction and piping of the UDDT. To limit scaling, all connections (pipes) to storage tanks should be kept as short as possible; whenever they exist, pipes should be installed with at least a 1% slope, and sharp angles (90°) should be avoided. A pipe diameter of 50 mm is sufficient for steep slopes and where maintenance is easy. Larger diameter pipes (> 75 mm) should be used elsewhere, especially for minimum slopes, and where access is difficult. To prevent odours from coming back up the pipe, an odour seal should be installed at the urine drain.

Appropriateness

The UDDT is simple to design and build, using such materials as concrete and wire mesh or plastic. The UDDT design can be altered to suit the needs of specific populations (i.e., smaller for children, people who prefer to squat, etc.).

Health Aspects/Acceptance

The UDDT is not intuitive or immediately obvious to some users. At first, users may be hesitant about using it, and mistakes made (e.g., faeces in the urine bowl) may deter others from accepting this type of toilet as well. Demonstration projects and training are essential to achieve good acceptance with users. For better acceptance of the system and to avoid urine in the faeces collection bowl, the toilet can be combined with a urinal, allowing men to stand and urinate.

Operation & Maintenance

A UDDT is slightly more difficult to keep clean compared to other toilets because of both the lack of water and the need to separate the solid faeces and liquid urine. No design will work for everyone and, therefore, some users may have difficulty separating both streams perfectly, which may result in extra cleaning and maintenance. Faeces can be accidentally deposited in the urine section, causing blockages and cleaning problems.
All of the surfaces should be cleaned regularly to prevent odours and to minimize the formation of stains. Water should not be poured in the toilet for cleaning. Instead, a damp cloth may be used to wipe down the seat and the inner bowls. Some toilets are easily removable and can be cleaned more thoroughly. It is important that the faeces remain separate and dry. When the toilet is cleaned with water, care should be taken to ensure that the faeces are not mixed with water.
Because urine is collected separately, calcium- and magnesium-based minerals and salts can precipitate and build up in pipes and on surfaces where urine is constantly present. Washing the bowl with a mild acid (e.g., vinegar) and/or hot water can prevent the build-up of mineral deposits and scaling. Stronger (> 24% acetic) acid or a caustic soda solution (2 parts water to 1 part soda) can be used for removing blockages. However, in some cases manual removal may be required.
An odour seal also requires occasional maintenance. It is critical to regularly check its functioning.

References

Further Readings

  • Cover image of a reference book or miscellany.

    CANADAY, C. (2011): Simple Urine-diverting Dry Toilets (UDDTs) Built with Recycled or Readily Available Materials. Pastaza: Omaere Ethnobotanical Park. URL [Accessed: 22.02.2012]. PDF

    The goal of this paper is to show that conversion to using UDDTs can be more a matter of shifting paradigms than capital investment. People can learn the concept and apply it on their own, with materials that they already have access to.

  • Cover image of a reference book or miscellany.

    ECOSAN CLUB (Editor) (2011): Toilets. Vienna: Ecosan Club. URL. PDF

    The first part of a sanitation system is the „user interface“, i.e. the toilet, pedestal, pan or urinal. It is an important part of the sanitation system because this is the part the user comes in contact with. Acceptance of a sanitation system therefore often mainly depends on the acceptance of the user interface. This paper gives an overview on developments of different technologies for user interfaces (UDDTs and urinals). The contributions present developments in different geographical regions: South America, East Africa and the Eastern Europe, the Caucasus and Central Asia (EECCA) countries.

  • Cover image of a reference book or miscellany.

    WAFLER, M. (2008): Assessment of Urine-Diversion Dehydration Toilet Designs with Respect to Construction Materials Used and Associated Costs. URL [Accessed: 07.07.2010]. PDF

    The document compiles the assessment of different UDDTs designs with respect to the construction materials used (e.g. country burned bricks, cement hollow blocks, ferro-cement, etc.) and their associated construction costs. Optimization and cost estimates are based upon the assessment of various designs of UDDTs applied in India and bills of quantity (BOQ).

Case Studies

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    KASSA, K. (2010): UDD Toilets for Nelson Mandela Private School, Arba Minch, Ethiopia. Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 11.08.2010]. PDF

    This case study reports replacement of pit latrines with a UDDT block (six single-vault UDDTs) for Nelson Mandela School, a private school from grade 1 to 9 with a total of 200 students and teachers, in Arba Minch, Ethiopia. The school staff operates and maintains the toilet (storage conditions of excreta, urine, hand washing facilities, cleaning of toilets, provision of drying agent like ash). The school janitor is responsible for providing the drying agents.

Awareness Material

Training Material

  • Cover image of a reference book or miscellany.

    DEEGENER, S.; SAMWEL, M.; WENDLAND, C. (Editor) (2015): Urine Diverting Dry Toilets. Principles, Operation and Construction. Women in Europe for a Common Future (WECF). URL [Accessed: 29.11.2015]. PDF

    This manual provides the background of ecological sanitation and gives guidance how to construct and operate a UDDT. The manual, originally published in 2006, has been revised based on the experiences of more than 10 years in 12 countries by WECF with local partners.

  • Cover image of a reference book or miscellany.

    ESF (Editor) (2009): Urine Diversion Dehydration Toilet (UDDT) - Construction Manual. Pune: Ecosan Services Foundation (ESF). URL [Accessed: 07.07.2010]. PDF

    Design and construction manual on that also provides information on the nutrient value of human urine and faecal matter, general hygiene aspects, the reuse of sanitized urine and faecal matter, and costs of various Indian UDDT designs.

  • Cover image of a reference book or miscellany.

    HOFFMANN, H. (2012): Construction of Bench Style Double Vault Urine Diversion Toilet and Alternatives. Lima: Rotaria del Peru SAC. URL [Accessed: 26.03.2012]. PDF

    The use of Urine Diversion (UD) in dry toilets allows faeces dehydration. Urine can be reused as urea, while faeces are dried in a double vault system of alternate use. The moisture comes out using ventilation pipes. After 2 years the end product can be emptied and reused without having any health risk. Water from washing can be treated in a constructed wetland and reused for instance for irrigation.

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