and treatment cartridge into a lower tank from which it could be decanted through a tap. The water
quality was checked by the testing device, and filter cartridges would be obtained and inserted depending on the test readout. In most areas, once the composition of the water was known, the same filter kits would be required each time. The capacity of the tank and filter system ranged from 20 litres, sufficient for a family for one day in rural conditions, up to 500 litres which could supply a small village through a supply pumped from a bore¬hole or diverted from a stream. Prototypes were built, tested in village conditions and improved until the system worked perfectly.