The availability of enough clean water is an essential condition for life on the planet, as stated by Goal # 6 of the United Nations’ Goals for Sustainable Development. Even if water is a relatively abundant compound on Earth, only a tiny fraction of the existing water is suitable for most of human needs. The chemical parameters that allow or forbid diverse water uses are discussed in the lecture. Highlights of 42 the contemporary analytical tools used for water testing are presented, together with some of the scientific and technological advances in the field of water quality improvement, both before and after consumption.