Water hardness in Fontenay-le-Fleury
17.8 °fH hard
Tap water in Fontenay-le-Fleury is hard: 17.8 °fH (178 mg/L · 10.4 gpg · 10 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 78242 (2026-08) · data checked 2026-10-19
Water in Fontenay-le-Fleury (Yvelines) is supplied by S.E.O.P. The ARS health-control data (SISE-Eaux, August 2026) give a measured hardness of 178 mg/L CaCO₃, which is hard.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 17.8 °fH |
|---|---|
| Utility | S.E.O.P. |
How Fontenay-le-Fleury compares
- Tap water in Fontenay-le-Fleury is 26 % softer than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 21964 of 33641 in France (1 = hardest); 35 % of these cities have softer water.
- In Yvelines it is number 204 of 222 cities; the regional median is 23 °fH.
- Nearest city with clearly softer water: Maisons-Laffitte, 16 km away (9.8 °fH).
- Nearest city with clearly harder water: Châteaufort, 9 km away (24.3 °fH).
Ranking of the hardest and softest water in France →
What it means at home
- Fast scale on taps, shower screens and kettle; white spots on glassware.
- Water heater: efficiency loss and element failures within years if unprotected.
- Dry skin and dull hair after showering are common.
- Softener recommended; jug or reverse osmosis for drinking.
How much salt will you use for softening?
Recommended, especially with a heater or boiler: scale cuts efficiency and shortens its life.
Descale a coffee machine or kettle about every 2 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Fontenay-le-Fleury
| Brand | Setting for this water |
|---|---|
| Bosch | H02 |
| Miele | 10 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S2 |
| LG | H2 |
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 Fontenay-le-Fleury water hard or soft?
It is hard: 178 mg/L as CaCO₃ (10.4 gpg, 10 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Fontenay-le-Fleury 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 Fontenay-le-Fleury water?
10.4 gpg, equal to 10 °dH, 17.8 °fH or 178 mg/L calcium carbonate.
What dishwasher salt setting should I use in Fontenay-le-Fleury?
For 178 mg/L (10 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Fontenay-le-Fleury?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
Source
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 78242 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 78242 · Outdated figure? Tell us