Water hardness in Castro-Urdiales
19 °fH very hard
Tap water in Castro-Urdiales is very hard: 19 °fH (190 mg/L · 11.1 gpg · 10.6 °dH).
Source: SINAC, Ministerio de Sanidad — Información de un abastecimiento, municipio 39020 (2026-07) · data checked 2026-10-19
Range across supply zones: 85–260 mg/L.
The water comes from rivers, reservoirs and springs on the Cantabrian slope, with limestone influence. Official analyses put the water at 190 mg/L CaCO₃, very hard, with values between 85 and 260 mg/L depending on network, source and season. Limestone and sedimentary rock dissolve plenty of calcium and magnesium, hence the high hardness. Scale deposits quickly in kettles, heaters and heating elements; many households fit a softener.
Fuentes españolas usan °fH (grados hidrotimétricos franceses) o mg/L CaCO₃.
Water data
| Total hardness | 19 °fH |
|---|
How Castro-Urdiales compares
- Tap water in Castro-Urdiales is 5 % softer than the median of the 4988 cities we track in Spain (20.1 °fH).
- By hardness it ranks 2608 of 4988 in Spain (1 = hardest); 47 % of these cities have softer water.
- In Cantabria it is number 5 of 50 cities; the regional median is 13.1 °fH.
- Nearest city with clearly softer water: Guriezo, 7 km away (14 °fH).
- Nearest city with clearly harder water: Hazas de Cesto, 28 km away (25.9 °fH).
Ranking of the hardest and softest water in Spain →
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 Castro-Urdiales
| Brand | Setting for this water |
|---|---|
| Bosch | H03 |
| Miele | 11 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S2 |
| LG | H2 |
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 Castro-Urdiales water hard or soft?
It is very hard: 190 mg/L as CaCO₃ (11.1 gpg, 10.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Castro-Urdiales safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Fuentes españolas usan °fH (grados hidrotimétricos franceses) o mg/L CaCO₃.
How many grains per gallon is Castro-Urdiales water?
11.1 gpg, equal to 10.6 °dH, 19 °fH or 190 mg/L calcium carbonate.
What dishwasher salt setting should I use in Castro-Urdiales?
For 190 mg/L (10.6 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Castro-Urdiales?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: SINAC, Ministerio de Sanidad — Información de un abastecimiento, municipio 39020 (2026-07). Method: own measurement. SINAC, Ministerio de Sanidad — Información de un abastecimiento, municipio 39020 · Outdated figure? Tell us