|Development of appropriate specifications for low cost technologies is not often done in a rigorous manner. This paper presents the use of systematic DMAIC methodology (Define, Measure, Analyze, Improve and Control) for arriving at practical specifications for the bacterial (E.coli) trapping level in a low cost water filter meant for rural needs in India. This filter is based upon a materials-based invention, viz. the use of the waste material, rice husk ash as a filtration medium to achieve near 99% trapping efficiency of E.coli bacteria. In actual practice, however, the filtered water shows substantial variation in bacterial levels when filters are produced in significant numbers. This variation is reduced to safe limits through systematic application of the DMAIC methodology. When the filters made by the villagers from the resulting process were introduced in a small village in India, significant reduction in the number of cases of water-borne diseases was reported. Since the materials on which this work was done are rice husk ash (largely silica), commonly occurring pebbles and ordinary Portland cement, all of which come under the broad category of ceramic materials, the methodology can be applied to the reduction of variation in ceramic processes and products wherever applicable.