Water hardness in Castres (Tarn)
10.2 °fH moderately hard
Tap water in Castres (Tarn) is moderately hard: 10.2 °fH (102 mg/L · 6 gpg · 5.7 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 81065 (2026-08) · data checked 2026-10-19
Around Castres, drinking water comes from the Agout and Montagne Noire resources, on crystalline bedrock. It is not very hard: 102.0 mg/L CaCO₃. Scale stays low.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 10.2 °fH |
|---|---|
| Utility | Spl Eaux De Castres Burlats |
How Castres (Tarn) compares
- Tap water in Castres (Tarn) is 57 % softer than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 28691 of 33641 in France (1 = hardest); 15 % of these cities have softer water.
- In Tarn it is number 127 of 314 cities; the regional median is 9.3 °fH.
- Nearest city with clearly softer water: Saint-Affrique-les-Montagnes, 8 km away (4.8 °fH).
- Nearest city with clearly harder water: Navès, 5 km away (16.8 °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 Castres
| 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 Castres (Tarn) water hard or soft?
It is moderately hard: 102 mg/L as CaCO₃ (6 gpg, 5.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Castres (Tarn) 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 Castres (Tarn) water?
6 gpg, equal to 5.7 °dH, 10.2 °fH or 102 mg/L calcium carbonate.
What dishwasher salt setting should I use in Castres (Tarn)?
For 102 mg/L (5.7 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Castres (Tarn)?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 81065 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 81065 · Outdated figure? Tell us