Low volume flush wc design

Water usage by w.c. flushing can represent a major portion of the total water use in a dwelling and may be sufficient to prevent the introduction of such sanitary facilities in developing country applications where water is in short supply. The work reported has concentrated upon the development of a low cost 3-litre flush volume w.c. suitable for use in developing countries and has been funded by the UK Overseas Development Ad­ministration (ODA). This paper presents the team's approach to the problem of low water use w.c. design, in terms of the modifiable variables such as trap volume, water seal depth, cistern to bowl water distribution etc. Laboratory trials are reported to support the design decisions taken in respect of trap seal depth and volume. In order to both reduce bowl cost and provide the bowl with a pour flush capability, the bowl is rimless. The solution to the water discharge to the bowl and subsequent surface cleansing problem chosen is a water spreading nozzle connected directly to the cistern discharge and posi­tioned at the rear of the bowl. Development of this "spreader bar" flow device is reported. Site evaluation in Botswana and Lesotho during 1985 and 1986 is also discussed.