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Overseas Development Administration (ODA), to design, develop and site-appraise a low-volume flush WC, with the cooperation of Caradon Twyfords Ltd (Bocarro, 1988). |
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Previous experience and discussions with ODA established the following criteria for the project: |
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1. A flush volume of 34.5 litres would be realistic. |
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2. A washdown pedestal P-trap WC pan flushed by an independent cistern fitted with a drop valve would offer the widest application. The potential to use locally available cisterns and components was essential to ensure availability of spare parts in the future. |
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3. The potential to offer a bucket/pour flush WC pan, upgradable to cistern flush, should be considered. The omission of a flushing rim, which could not be cleaned by pour-flushing, would then be necessary and an alternative method of flush water distribution developed (in fact this pour-flush development was little used and further discussion of it is omitted in this chapter). |
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4. The necessity for simplicity of design and operation to ensure adequate maintenance of the WC. This ruled out systems such as vacuum- or pressure-assisted solids transportation, siphon break-valves and diaphragms. |
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5. The predominance of single storey housing and buildings in developing countries minimizes pressure fluctuations in the drainage system and would allow reduced trap-seal depth, subject to evaporative loss constraints. |
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6. Gaborone in Botswana and Maseru in Lesotho would be used for site evaluation of the low-volume flush toilet (LVFT) under a wide range of conditions. |
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This chapter presents the research and development necessary to produce an appliance within these guidelines, together with an overview of its site evaluation in Botswana, where the installation conditions were closest to those in the UK. |
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