The surveillance system for waterborne acute gastroenteritis outbreaks developed by Santé publique France was tested in real-world conditions across seven departments in collaboration with relevant stakeholders. Outbreaks confined to a specific tap water distribution unit (UDI) are automatically detected using data from the national health insurance system and the SISE-Eaux database. Their waterborne origin is confirmed by environmental investigations conducted by regional health agencies on the affected WDSs. A method has been established to classify their waterborne plausibility as “strong,” “probable,” “possible,” or “undetermined origin.” This report presents a new approach to managing the microbiological quality of tap water in France. The method increases the detection rate of outbreaks tenfold, with 67 outbreaks sharing the same UDI compared to 2 that were reported to health authorities at the time of their occurrence. Half of the environmental investigations identified an event that could have led to accidental contamination of the water systems. Water-borne plausibility was classified as probable or high for 25% of the outbreaks. Following this study, the deployment of a water-borne outbreak surveillance system across all French departments is feasible. This system should align perfectly with international and national objectives promoted by the WHO, which aim to complement surveillance based on the quality of distributed water with a quality system based on the assessment and monitoring of risk factors (drinking water management and safety plans).