Treatment of drinking water at the household level is one of the most effective preventive interventions against diarrhea, a leading cause of illness and death among children in developing countries. A pilot project in two districts in Rwanda aimed to increase use of Sûr’Eau, a chlorine solution for drinking water treatment, through a partnership between community-based health insurance schemes and community health workers who promoted and distributed the product. Evaluation of the pilot, drawing on a difference-in-differences design and data from pre- and post-pilot household surveys of 4,780 households, showed that after 18 months of pilot implementation, knowledge and use of the product increased significantly in two pilot districts, but remained unchanged in a control district. The pilot was associated with a 40–42 percentage point increase in ever use, and 8–9 percentage points increase in use of Sûr’Eau at time of the survey (self-reported measures). Our data suggest that exposure to inter-personal communication on Sûr’Eau and hearing about the product at community meetings and health centers were associated with an increase in use.