Water hardness in São Domingos de Rana
108 mg/L moderately hard
Tap water in São Domingos de Rana is moderately hard: 108 mg/L (6.3 gpg · 6 °dH · 10.8 °fH).
Source: Águas de Cascais - Relatório trimestral da qualidade da água - Geral, 2º trimestre 2026 (2026) · data checked 2026-10-23
Range across supply zones: 52–163 mg/L.
São Domingos de Rana is supplied by its local water utility. Northern and central Portugal sit largely on granite and schist, which gives soft water, while limestone in the south and centre makes it harder. The reported hardness is 107.5 mg/L CaCO₃, with measurements from 52.0 to 163.0 mg/L. Limescale appears gradually on taps and heating elements; occasional descaling keeps it in check.
Portuguese operators report "dureza total" in mg/L CaCO₃ to ERSAR.
Water data
| Total hardness | 108 mg/L |
|---|---|
| Utility | Águas de Cascais |
How São Domingos de Rana compares
- Tap water in São Domingos de Rana is 29 % harder than the median of the 77 cities we track in Portugal (83 mg/L).
- By hardness it ranks 11 of 77 in Portugal (1 = hardest); 87 % of these cities have softer water.
- In Lisboa it is number 2 of 13 cities; the regional median is 50 mg/L.
- Nearest city with clearly softer water: Oeiras, 3 km away (42 mg/L).
- Nearest city with clearly harder water: Alcabideche, 7 km away (289 mg/L).
Ranking of the hardest and softest water in Portugal →
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 São Domingos de Rana
| 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 São Domingos de Rana water hard or soft?
It is moderately hard: 108 mg/L as CaCO₃ (6.3 gpg, 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 São Domingos de Rana safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Portuguese operators report "dureza total" in mg/L CaCO₃ to ERSAR.
How many grains per gallon is São Domingos de Rana water?
6.3 gpg, equal to 6 °dH, 10.8 °fH or 108 mg/L calcium carbonate.
What dishwasher salt setting should I use in São Domingos de Rana?
For 108 mg/L (6 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in São Domingos de Rana?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: Águas de Cascais - Relatório trimestral da qualidade da água - Geral, 2º trimestre 2026 (2026). Method: computed from supplier's calcium and magnesium. Águas de Cascais - Relatório trimestral da qualidade da água - Geral, 2º trimestre 2026 · Outdated figure? Tell us