As climate change and rapid urbanization stress our aging water infrastructure, cities are under increasing pressure to develop more flexible, resilient, and modular water management systems. In response, onsite water reuse practices have been adopted by several cities globally. In addition to technological innovation, these novel water treatment systems also require new stakeholder collaborations, relationships, and processes to support them. There are, however, few models for stakeholder arrangements that support and encourage the adoption and success of such infrastructure. In this paper, we use interviews with stakeholders involved in onsite water reuse projects in the San Francisco Bay Area to create a social network map that describes the interactions between stakeholders at large and during specific phases of project implementation. Using qualitative content analysis of expert interviews and social network analysis, we identify four actor roles that are key to the functioning of this novel water infrastructure paradigm�specialists, continuity providers, program champions, and conveners�and discuss the importance of each role through the course of project implementation. These findings can be helpful for policy interventions and outreach efforts by other cities and communities looking to implement onsite water systems.