Water hardness in Lannion
10 °fH moderately hard
Tap water in Lannion is moderately hard: 10 °fH (100 mg/L · 5.8 gpg · 5.6 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 22113 (2026-08) · data checked 2026-10-19
Range across supply zones: 86–110 mg/L.
Lannion is supplied by Lannion-Trégor Communauté in Brittany, where water comes mostly from rivers and reservoirs on granite and schist. Those rocks release little limestone: 100 mg/L CaCO₃, ranging from 86 to 110 mg/L. The water is moderately hard and scale is limited.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 10 °fH |
|---|---|
| Utility | Ca Lannion-Trégor Communauté |
How Lannion compares
- Tap water in Lannion is 58 % softer than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 28827 of 33641 in France (1 = hardest); 14 % of these cities have softer water.
- In Côtes-d'Armor it is number 255 of 295 cities; the regional median is 13 °fH.
- Nearest city with clearly softer water: Plougonven, 30 km away (6.3 °fH).
- Nearest city with clearly harder water: Rospez, 5 km away (13.5 °fH).
Ranking of the hardest and softest water in France →
What it means at home
- Visible kettle scale every few weeks; vinegar or citric acid is enough.
- Water heater and washing machine: some long-term scale; a scale inhibitor slows it.
- Dishwasher: medium salt setting.
- Softener optional; pays off mainly with a gas boiler or tankless heater.
How much salt will you use for softening?
Optional. A scale inhibitor or a small softener protects the heater; soap savings are modest.
Descale a coffee machine or kettle about every 3 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Lannion
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 6 °dH |
| AEG / Electrolux | 2 |
| Beko | 2nd |
| Hoover | S1 |
| LG | H1 |
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 Lannion water hard or soft?
It is moderately hard: 100 mg/L as CaCO₃ (5.8 gpg, 5.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Lannion 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 Lannion water?
5.8 gpg, equal to 5.6 °dH, 10 °fH or 100 mg/L calcium carbonate.
What dishwasher salt setting should I use in Lannion?
For 100 mg/L (5.6 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Lannion?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 22113 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 22113 · Outdated figure? Tell us