Water hardness in Triel-sur-Seine
21.9 °fH very hard
Tap water in Triel-sur-Seine is very hard: 21.9 °fH (219 mg/L · 12.8 gpg · 12.3 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 78624 (2026-08) · data checked 2026-10-19
Range across supply zones: 94–344 mg/L.
Triel-sur-Seine (Yvelines) is served by the Société des Eaux de Fin d'Oise. Median hardness is 219 mg/L as CaCO₃, but the spread is very wide, from 94 to 344 mg/L across measurements. It is classed as very hard. Source: SISE-Eaux health control (ARS, commune 78624), August 2026.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 21.9 °fH |
|---|---|
| Utility | Societe Des Eaux De Fin D'Oise |
How Triel-sur-Seine compares
- Tap water in Triel-sur-Seine is 8 % softer than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 18845 of 33641 in France (1 = hardest); 44 % of these cities have softer water.
- In Yvelines it is number 151 of 222 cities; the regional median is 23 °fH.
- Nearest city with clearly softer water: Maisons-Laffitte, 11 km away (9.8 °fH).
- Nearest city with clearly harder water: Chanteloup-les-Vignes, 2 km away (34.4 °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 Triel-sur-Seine
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 12 °dH |
| AEG / Electrolux | 3 |
| 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 Triel-sur-Seine water hard or soft?
It is very hard: 219 mg/L as CaCO₃ (12.8 gpg, 12.3 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Triel-sur-Seine 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 Triel-sur-Seine water?
12.8 gpg, equal to 12.3 °dH, 21.9 °fH or 219 mg/L calcium carbonate.
What dishwasher salt setting should I use in Triel-sur-Seine?
For 219 mg/L (12.3 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Triel-sur-Seine?
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 78624 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 78624 · Outdated figure? Tell us