Highly sophisticated management and water treatment techniques are needed to serve the Paris metropolitan area with potable water. Most of the suburbs depend on supplies from the Seine, the Marne, and the Oise rivers, all of which are subject to the pollutants and accidental spills inherent in a densely populated industrial area. Privately operated water utilities serving the suburbs have responded with a variety of safeguards, including automated monitoring systems that allow immediate adjustments to be made in water treatment plants, interconnections among sources and municipalities, and state‐of‐the‐art treatment techniques. The authors describe the complexities and the challenges of providing high quality drinking water from low quality sources for the most densely populated region of France.