Dureté de l'eau à Paris

Paris tap water, supplied by Eau de Paris, registers at approximately 234 mg/L of calcium carbonate — classifying it as hard water by all major European standards. Paris draws from two distinct sources: surface water intakes on the Seine (at Orly) and Marne rivers, and deep groundwater from chalk aquifers (the Albien and Néocomien formations) beneath the Paris Basin. The chalk geology of the Île-de-France region is directly responsible for the high mineral content, as water percolating through Cretaceous chalk dissolves substantial calcium carbonate before reaching the aquifer.

For Parisian households, hard water has a visible impact. Limescale forms rapidly on kettle elements and shower heads (calcaire in French) — a familiar domestic complaint across the city. Dishwashers in Paris should be set to a high salt setting (level 4–5), and coffee machine descaling is required more frequently than in softer-water cities. Eau de Paris reports seasonal variation: groundwater used during summer peak demand is typically harder than blended winter supply.

Despite its hardness, Paris tap water (l'eau du robinet) is of excellent quality and is safe to drink directly from the tap. It is subject to daily quality testing at over 400 points across the distribution network and consistently meets all EU Drinking Water Directive standards. The hardness does contribute a slight mineral taste that some residents mask with filtration pitchers.