Water hardness in Lille
37.6 °fH very hard
Tap water in Lille is very hard: 37.6 °fH (376 mg/L · 22 gpg · 21.1 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 59350 (2026-08) · data checked 2026-10-19
Range across supply zones: 359–379 mg/L.
In the Lille metropolitan area, water production relies mainly on boreholes in the chalk aquifer to the south and in carboniferous limestone to the north. Chalk gives water heavily loaded with lime: 376.0 mg/L CaCO₃, between 359.0 and 379.0 mg/L. Scale forms very quickly, and a softener is often considered.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 37.6 °fH |
|---|---|
| Utility | Ileo; Sourceo |
How Lille compares
- Tap water in Lille is 57 % harder than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 1544 of 33641 in France (1 = hardest); 95 % of these cities have softer water.
- In Nord it is number 229 of 634 cities; the regional median is 35.8 °fH.
- Nearest city with clearly softer water: Lompret, 6 km away (29.3 °fH).
- Nearest city with clearly harder water: Escobecques, 9 km away (48.7 °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 Lille
| Brand | Setting for this water |
|---|---|
| Bosch | H06 |
| Miele | 21 °dH |
| AEG / Electrolux | 5 |
| Beko | 6th |
| Hoover | S3 |
| LG | H4 |
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 Lille water hard or soft?
It is very hard: 376 mg/L as CaCO₃ (22 gpg, 21.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Lille 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 Lille water?
22 gpg, equal to 21.1 °dH, 37.6 °fH or 376 mg/L calcium carbonate.
What dishwasher salt setting should I use in Lille?
For 376 mg/L (21.1 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Lille?
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 59350 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 59350 · Outdated figure? Tell us