By now, all UN Member States have recognized the human rights to water and sanitation by supporting one or more international documents, such as resolutions or declarations. The WASH sector increasingly welcomes the human rights to water and sanitation as a concept. Yet important questions and misunderstandings persist. One of them is an often limited understanding of the human rights principle of equality - and why it is preferable to other concepts such as equity. This paper explains the importance of the human rights principle of equality for achieving meaningful progress in the realization of the human rights to water and sanitation. It sets out what international human rights law demands and how this relates to national legal frameworks for water and sanitation services. Using a number of examples, it shows how equality has been used to address cases of discrimination and to tackle existing inequalities in water and sanitation service provision in a targeted manner.