|
|
|
|
|
|
|
13.2 Laboratory Development of the Low-Volume Flush Toilet |
|
|
|
|
|
|
|
|
A P-trap WC configuration was adopted, to conform to common practice in developing countries. The modelling of the LVFT was based on a Twyfords British Standard 1213 P-trap WC from which both the flushing rim and trap-seal back plate had been removed. Plasticine was used to remodel the internal shape of the bowl and trap, and perspex back plates were fitted to vary trapseal depth. A mechanical tipping bucket was developed to provide repeatable and representative pour-flushing by bucket. In addition to British Standard 5503 tests, which included the ball test, paper test and sawdust test, a range of discriminatory tests were used and developed to appraise WC performance. |
|
|
|
|
|
|
|
|
1. Multiple ball test, using fifty 20 mm diameter balls of the same specific gravity which could be selected in the range 0.85-1.15. Discharge efficiency was calculated as the percentage of balls discharging successfully. |
|
|
|
|
|
|
|
|
2. Liquid contamination test, using potassium permanganate to simulate liquid contamination of the WC trap. Light absorption, measured by a colorimeter, of a sample of trap-water taken after flushing compared with a sample taken before flushing, and calculated as a percentage relative residual concentration, gives an important measure of flushing performance. |
|
|
|
|
|
|
|
|
3. Modified paper test, using six pieces of 125 ´ 125 mm newspaper. |
|
|
|
|
|
|
|
|
4. Simulated faeces test, using three 30 mm diameter by 100 mm long foamed plastic stools having a saturated specific gravity of 0.98. |
|
|
|
|
|
|
|
|
5. Modified ball test, using the BS5503 ball but recording the amount of water discharged ahead of the ball relative to the flush volume. This modification produced a useful degree of discrimination. |
|
|
|
|
|
|
|
|
6. Various bowl washing tests, including the American ANSI A112.19.2M (1982) test, which involves drawing a horizontal |
|
|
|
|
|