Water hardness in Calais
28.8 °fH very hard
Tap water in Calais is very hard: 28.8 °fH (288 mg/L · 16.8 gpg · 16.1 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 62193 (2026-08) · data checked 2026-10-19
In the Calaisis, drinking water comes from the chalk aquifer of Artois and the Boulonnais. Chalk is almost pure limestone: 288.0 mg/L CaCO₃. Scale is a common problem for kettles and machines.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 28.8 °fH |
|---|---|
| Utility | Suez Eau France - Calais |
How Calais compares
- Tap water in Calais is 21 % harder than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 10268 of 33641 in France (1 = hardest); 69 % of these cities have softer water.
- In Pas-de-Calais it is number 786 of 880 cities; the regional median is 32.9 °fH.
- Nearest city with clearly softer water: Grand-Fort-Philippe, 19 km away (21 °fH).
- Nearest city with clearly harder water: Alincthun, 24 km away (38.4 °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 Calais
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 16 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| Hoover | S2 |
| 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 Calais water hard or soft?
It is very hard: 288 mg/L as CaCO₃ (16.8 gpg, 16.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Calais 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 Calais water?
16.8 gpg, equal to 16.1 °dH, 28.8 °fH or 288 mg/L calcium carbonate.
What dishwasher salt setting should I use in Calais?
For 288 mg/L (16.1 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Calais?
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 62193 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 62193 · Outdated figure? Tell us