Water hardness in L'Isle-Adam
31.4 °fH very hard
Tap water in L'Isle-Adam is very hard: 31.4 °fH (314 mg/L · 18.3 gpg · 17.6 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 95313 (2026-06) · data checked 2026-10-19
In L'Isle-Adam (Val-d'Oise), water comes from the operator Ceg. The published hardness is 314 mg/L CaCO₃, in the very hard category. The value is measured, from the ARS SISE-Eaux health monitoring, June 2026.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 31.4 °fH |
|---|---|
| Utility | Ceg |
How L'Isle-Adam compares
- Tap water in L'Isle-Adam is 31 % harder than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 6554 of 33641 in France (1 = hardest); 80 % of these cities have softer water.
- In Val-d'Oise it is number 68 of 149 cities; the regional median is 30.6 °fH.
- Nearest city with clearly softer water: Nerville-la-Forêt, 5 km away (19.7 °fH).
- Nearest city with clearly harder water: Hérouville-en-Vexin, 7 km away (40.2 °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 L'Isle-Adam
| Brand | Setting for this water |
|---|---|
| Bosch | H05 |
| Miele | 18 °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 L'Isle-Adam water hard or soft?
It is very hard: 314 mg/L as CaCO₃ (18.3 gpg, 17.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in L'Isle-Adam 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 L'Isle-Adam water?
18.3 gpg, equal to 17.6 °dH, 31.4 °fH or 314 mg/L calcium carbonate.
What dishwasher salt setting should I use in L'Isle-Adam?
For 314 mg/L (17.6 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in L'Isle-Adam?
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 95313 (2026-06). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 95313 · Outdated figure? Tell us