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parameter should be as low as possible, subject to certain physical limitations. It was decided to adopt a minimum trap passage width (w) of 63 mm in order to meet dietary constraints. Consideration of drain pressure fluctuation and trap-seal evaporative loss suggested that trap-seal depth (h) could be safely reduced from 50 to 36 mm. These two limitations dictated a minimum trap volume (S) of approximately 0.86 litres. The value of the dimensionless parameter (Sh/Fw) for the Mark 0 WC with 9.1 litre flush is 0.143 (Figure 13.6). Substituting the limits suggested above would require a flush volume (F) of 3.4 litres to attain similar WC performance, a prediction confirmed by the tests mentioned above. |
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13.3
Site Trials in Botswana |
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Caradon Twyfords (Stoke on Trent, UK) produced 220 of the Mark III WC pans (Figure 13.6), and 220 Mark VI diverter bars |
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Figure 13.7
The Mark VI PVC diverter bar |
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