Within the framework for the realization of the human right to water and sanitation, States have the obligation to implement programs and public policies that satisfy the basic needs of their population, especially its most vulnerable demographics. In Colombia, this challenge has been addressed through policies that provide a determined essential amount of free water to people whose access to water and sanitation services are limited due to low income. Through a review of legal and technical documents as well as relevant literature, this article presents an analysis of the particular determinants involved in implementing this program in Bogotá and Medellín, as well as some related concerns. Among such factors, we discuss the evolution and changes of the tariff model used in service provision, estimates of basic consumption, the role of social movements and collective action, and user disconnection due to non-payment. The main particularities and differences of each case highlighted the inconveniences related to the method of identifying eligible users and applying assistance to beneficiary user groups, and the need for national guidelines in implementing this policy.