Water hardness in Aulnay-sous-Bois
29.9 °fH very hard
Tap water in Aulnay-sous-Bois is very hard: 29.9 °fH (299 mg/L · 17.5 gpg · 16.8 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 93005 (2026-08) · data checked 2026-10-19
Range across supply zones: 280–318 mg/L.
Aulnay-sous-Bois is served by SEDIF, whose water comes mainly from the Seine, the Marne and the Oise, treated at the Choisy-le-Roi, Neuilly-sur-Marne and Méry-sur-Oise plants. The limestone of the Paris Basin crossed by these rivers gives 299.0 mg/L CaCO₃ at the median, between 280.0 and 318.0 mg/L depending on the measurement point. It is hard water that leaves deposits on shower heads.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 29.9 °fH |
|---|---|
| Utility | Franciliane |
How Aulnay-sous-Bois compares
- Tap water in Aulnay-sous-Bois is 25 % harder than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 8720 of 33641 in France (1 = hardest); 74 % of these cities have softer water.
- In Seine-Saint-Denis it is number 2 of 39 cities; the regional median is 28 °fH.
- Nearest city with clearly softer water: Sarcelles, 11 km away (19.5 °fH).
- Nearest city with clearly harder water: Vaudherland, 7 km away (41.3 °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 Aulnay-sous-Bois
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 17 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| Hoover | S3 |
| 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 Aulnay-sous-Bois water hard or soft?
It is very hard: 299 mg/L as CaCO₃ (17.5 gpg, 16.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Aulnay-sous-Bois 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 Aulnay-sous-Bois water?
17.5 gpg, equal to 16.8 °dH, 29.9 °fH or 299 mg/L calcium carbonate.
What dishwasher salt setting should I use in Aulnay-sous-Bois?
For 299 mg/L (16.8 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Aulnay-sous-Bois?
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 93005 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 93005 · Outdated figure? Tell us