Water hardness in Siero
10.1 °fH moderately hard
Tap water in Siero is moderately hard: 10.1 °fH (101 mg/L · 5.9 gpg · 5.7 °dH).
Source: SINAC, Ministerio de Sanidad — Información de un abastecimiento, municipio 33066 (2026-10) · data checked 2026-10-19
Range across supply zones: 89–237 mg/L.
The water comes from rivers and reservoirs on the Cantabrian slope, over limestone or siliceous rock depending on the valley. Official analyses put the water at 101 mg/L CaCO₃, moderately hard, with values between 89 and 237 mg/L depending on network, source and season. A mix of sources with different mineral content gives an intermediate value. Scale appears gradually on kettles and shower screens.
Fuentes españolas usan °fH (grados hidrotimétricos franceses) o mg/L CaCO₃.
Water data
| Total hardness | 10.1 °fH |
|---|
How Siero compares
- Tap water in Siero is 50 % softer than the median of the 4988 cities we track in Spain (20.1 °fH).
- By hardness it ranks 3563 of 4988 in Spain (1 = hardest); 28 % of these cities have softer water.
- In Asturias it is number 30 of 49 cities; the regional median is 11.5 °fH.
- Nearest city with clearly softer water: Muros de Nalón, 40 km away (4 °fH).
- Nearest city with clearly harder water: Sariego, 9 km away (22.6 °fH).
Ranking of the hardest and softest water in Spain →
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 Siero
| 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 Siero water hard or soft?
It is moderately hard: 101 mg/L as CaCO₃ (5.9 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 Siero 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 Siero water?
5.9 gpg, equal to 5.7 °dH, 10.1 °fH or 101 mg/L calcium carbonate.
What dishwasher salt setting should I use in Siero?
For 101 mg/L (5.7 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Siero?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: SINAC, Ministerio de Sanidad — Información de un abastecimiento, municipio 33066 (2026-10). Method: own measurement. SINAC, Ministerio de Sanidad — Información de un abastecimiento, municipio 33066 · Outdated figure? Tell us