The paper will explore how investigations of purity or water, both of natural sources and in the municipality reservoirs in urban centres was a key project in public health policies as well as in the application of chemistry and bacteriology in colonial India. By the nineteenth century, through repeated outbreaks of cholera and other water related diseases, water resources in India had become a topic of intense discussion and debate among colonial medical officers and administrators.by the nineteenth century, with the setting up of the municipalities, the supply of clean water for urban areas had also become an important concern in India. The paper will explore how the sciences of investigation of the purity of the natural water resources and the technologies adopted to purify water and supply clean and piped water in India developed in conjunction with changing ideas of tropical climate and environment as well as with the adoption of new scientific methods.