Is tap water in Switzerland really clean?

In Switzerland, drinking water must not exceed 40 mg/L of nitrates, and the groundwater used to produce it 25 mg/L. In intensive farming areas, the situation is a cause for concern: around one groundwater monitoring station in six exceeds 25 mg/L, and more than half in arable farming regions. More than 80% of stations on the Swiss Plateau record concentrations above 10 mg/L.¹

The most exposed cantons are Vaud, Fribourg, Bern and parts of Thurgau and Aargau, where intensive farming is concentrated. Excess nitrates are particularly problematic for infants under 6 months, as they interfere with the transport of oxygen in the blood.

In 2025, analyses in the cantons of Geneva and Vaud detected 1,2,4-triazole (a fungicide metabolite) at concentrations exceeding federal requirements in networks supplied by Lake Geneva.⁴ It is not the active molecule that is detected, but what it turns into after breaking down in the environment.

In response, the Federal Council opened a consultation in 2025 to tighten limit values for pesticides. Currently, only 19 substances are covered by ecotoxicological limit values, a fraction of what is actually used and detectable in water.⁴

In 2023, the Association of Cantonal Chemists of Switzerland (ACCS) analysed 564 drinking water samples covering around 70% of the Swiss population. Result: 54% of samples contained no detectable PFAS, which is reassuring. But 46% contained measurable levels, and 0.9% already exceeded the European limit of 0.1 µg/L, which has applied in the European Union since January 2026 but is not yet binding in Switzerland.²

The most worrying point: 99% of samples contained trifluoroacetic acid (TFA), a little-known PFAS resulting from the breakdown of certain pesticides and refrigerants. Its health risks are currently being assessed by the European agency EFSA.²

Limescale is not dangerous to health: it is even a source of calcium and magnesium. But very hard water (common in German-speaking Switzerland and on the Plateau, often above 25 to 30 °fH) leaves deposits on household appliances, pipes and coffee machines, and affects the taste. It is the main reason most Swiss households filter their water.

Added deliberately to maintain the microbiological quality of the water in the pipes. Harmless at the doses used, but responsible for the characteristic taste and smell that many people dislike. A simple activated carbon filter removes it effectively.