Water hardness in Gujan-Mestras
8.4 °fH moderately hard
Tap water in Gujan-Mestras is moderately hard: 8.4 °fH (84 mg/L · 4.9 gpg · 4.7 °dH).
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 33199 (2026-08) · data checked 2026-10-19
In Gujan-Mestras the water is supplied by So'Bass. The ARS health monitoring (SISE-Eaux, August 2026) gives 84 mg/L CaCO₃, or 8.4 °f: moderately hard water, based on measurements. At this level limescale is less of a nuisance than with very hard water.
TH en °fH : douce < 15, moyennement dure 15–25, dure 25–35, très dure > 35 °fH (classes usuelles ARS).
Water data
| Total hardness | 8.4 °fH |
|---|---|
| Utility | So'Bass |
How Gujan-Mestras compares
- Tap water in Gujan-Mestras is 65 % softer than the median of the 33641 cities we track in France (23.9 °fH).
- By hardness it ranks 30218 of 33641 in France (1 = hardest); 10 % of these cities have softer water.
- In Gironde it is number 530 of 534 cities; the regional median is 17.5 °fH.
- Nearest city with clearly softer water: Pontenx-les-Forges, 44 km away (5.8 °fH).
- Nearest city with clearly harder water: Mios, 11 km away (12.9 °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 Gujan-Mestras
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °dH |
| AEG / Electrolux | 2 |
| Beko | 1st |
| 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 Gujan-Mestras water hard or soft?
It is moderately hard: 84 mg/L as CaCO₃ (4.9 gpg, 4.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Gujan-Mestras 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 Gujan-Mestras water?
4.9 gpg, equal to 4.7 °dH, 8.4 °fH or 84 mg/L calcium carbonate.
What dishwasher salt setting should I use in Gujan-Mestras?
For 84 mg/L (4.7 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Gujan-Mestras?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 33199 (2026-08). Method: own measurement. Ministère de la Santé (ARS), contrôle sanitaire SISE-Eaux, commune 33199 · Outdated figure? Tell us