Water hardness in Porto
96 mg/L moderately hard
Tap water in Porto is moderately hard: 96 mg/L (5.6 gpg · 5.4 °dH · 9.6 °fH).
Source: ADP - Qualidade da água para consumo humano, 2.º trimestre 2026 (Porto) (2026-08) · data checked 2026-10-21
Porto's figure of 96 mg/L CaCO₃ comes from Águas do Douro e Paiva (ADP), whose quarterly report for Q2 2026 prints a single hardness analysis for the municipality. One sample is a snapshot, not an average, so treat it as indicative. At this level water is moderate: scale builds up slowly, but a kettle will still show a film over time.
Portuguese operators report "dureza total" in mg/L CaCO₃ to ERSAR.
Water data
| Total hardness | 96 mg/L |
|---|---|
| Utility | Águas do Douro e Paiva (ADP), concelho Porto |
How Porto compares
- Tap water in Porto is 15 % harder than the median of the 77 cities we track in Portugal (83 mg/L).
- By hardness it ranks 25 of 77 in Portugal (1 = hardest); 67 % of these cities have softer water.
- In 17 it is number 2 of 3 cities; the regional median is 96 mg/L.
- Nearest city with clearly softer water: Penafiel, 28 km away (55 mg/L).
- Nearest city with clearly harder water: Espinho, 16 km away (122 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 Porto
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 5 °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 Porto water hard or soft?
It is moderately hard: 96 mg/L as CaCO₃ (5.6 gpg, 5.4 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Porto 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 Porto water?
5.6 gpg, equal to 5.4 °dH, 9.6 °fH or 96 mg/L calcium carbonate.
What dishwasher salt setting should I use in Porto?
For 96 mg/L (5.4 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Porto?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: ADP - Qualidade da água para consumo humano, 2.º trimestre 2026 (Porto) (2026-08). Method: figure published by the water supplier. ADP - Qualidade da água para consumo humano, 2.º trimestre 2026 (Porto) · Outdated figure? Tell us