Water hardness in Chilly-Mazarin
27.1 °fH very hard
Tap water in Chilly-Mazarin is very hard: 27.1 °fH (271 mg/L · 15.8 gpg · 15.2 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 91161 (2026-08) · data checked 2026-10-19
Chilly-Mazarin in Essonne is supplied by Suez Eau France. In the Paris region, drinking water comes mostly from the Seine, Marne and Oise, treated at plants, and Paris Basin limestone gives it 271 mg/L CaCO₃. Very hard water scales kettles and shower heads quickly.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 27.1 °fH |
|---|---|
| Utility | Suez Eau France |
How Chilly-Mazarin compares
- Tap water in Chilly-Mazarin is 13 % harder than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 12713 of 33641 in France (1 = hardest); 62 % of these cities have softer water.
- In Essonne it is number 72 of 194 cities; the regional median is 25.9 °fH.
- Nearest city with clearly softer water: Villebon-sur-Yvette, 5 km away (19 °fH).
- Nearest city with clearly harder water: Bruyères-le-Châtel, 15 km away (38.3 °fH).
Ranking of the hardest and softest water in France →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Chilly-Mazarin
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 15 °dH |
| AEG / Electrolux | 4 |
| Beko | 4th |
| Hoover | S2 |
| LG | H3 |
From each brand's manual for the model family named in the source; your model may differ, so check its manual. All brands and how to change the setting →
FAQ
Is Chilly-Mazarin water hard or soft?
It is very hard: 271 mg/L as CaCO₃ (15.8 gpg, 15.2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Chilly-Mazarin safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
How many grains per gallon is Chilly-Mazarin water?
15.8 gpg, equal to 15.2 °dH, 27.1 °fH or 271 mg/L calcium carbonate.
What dishwasher salt setting should I use in Chilly-Mazarin?
For 271 mg/L (15.2 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Chilly-Mazarin?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 91161 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 91161 · Outdated figure? Tell us