The article describes, for the first time, the nature and timing of the introduction of filtration and chlorination of water for human consumption in Chile. Both were essential processes to ensure the drinkability of the piped water delivered to the population, as well as in the battle to avoid high rates of general and infant mortality. Between the mid-1920s and early 1930s, the Chilean state ensured almost universal chlorination of piped water, while filtration works involved a longer period, mainly during the first half of the 20th century. Our new evidence shows that the mortality rate of diseases associated to the ingestion of non-potable water, such as typhoid fever and dysentery, fell dramatically when water filtering and chlorination began in Chile, except in rural areas that were excluded from the provision of piped water.