Moving towards sustainable urban development leads to applying new forms of drainage, which provide multiple technical and social benefits to the community. However, in countries like Chile, there is still a large gap regarding methodologies to assess the social sustainability of projects in this area. Using a qualitative content analysis applied to experts’ interviews (n = 11), this study aims at (1) identifying metrics to assess the social sustainability of urban drainage systems; (2) identifying challenges for the implementation of such metrics, and (3) proposing changes to the current system, to assess urban drainage systems that enhance the integration of social sustainability within these systems. The results show that experts proposed metrics that may assess social sustainability, but in practice, these metrics are difficult to quantify. In terms of challenges, the fragmentation of responsibilities from organizations that are involved in managing urban drainage systems may complicate the use of new social sustainability metrics. Ultimately, it is suggested that an institution is created that can manage urban drainage systems using an integrative approach, to account for the benefits of social sustainability of urban drainage systems. These results can be used by authorities and decision-makers who work with urban drainage systems, to move towards methodologies that consider the benefits of social sustainability.