Water hardness in Rambouillet
23.6 °fH very hard
Tap water in Rambouillet is very hard: 23.6 °fH (236 mg/L · 13.8 gpg · 13.2 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 78517 (2026-07) · data checked 2026-10-19
Rambouillet (Yvelines) is served by Sefo, Rambouillet agency. The ARS health control (SISE-Eaux, commune 78517, July 2026) measures 236 mg/L CaCO₃. The water is classed as very hard.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 23.6 °fH |
|---|---|
| Utility | Sefo - Agence Rambouillet |
How Rambouillet compares
- Tap water in Rambouillet is close to the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 17069 of 33641 in France (1 = hardest); 49 % of these cities have softer water.
- In Yvelines it is number 83 of 222 cities; the regional median is 23 °fH.
- Nearest city with clearly softer water: Les Bréviaires, 7 km away (17.4 °fH).
- Nearest city with clearly harder water: Gazeran, 4 km away (29.6 °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 Rambouillet
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 13 °dH |
| AEG / Electrolux | 3 |
| Beko | 4th |
| 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 Rambouillet water hard or soft?
It is very hard: 236 mg/L as CaCO₃ (13.8 gpg, 13.2 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Rambouillet 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 Rambouillet water?
13.8 gpg, equal to 13.2 °dH, 23.6 °fH or 236 mg/L calcium carbonate.
What dishwasher salt setting should I use in Rambouillet?
For 236 mg/L (13.2 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Rambouillet?
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 78517 (2026-07). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 78517 · Outdated figure? Tell us