Water hardness in Ostrava
0.87 mmol/L moderately hard
Tap water in Ostrava is moderately hard: 0.87 mmol/L (87 mg/L · 5.1 gpg · 4.9 °dH).
Source: OVaK, Ostravské vodárny a kanalizace, a.s. (2026-10) · data checked 2026-10-21
Range across supply zones: 55–216 mg/L.
OVaK publishes hardness for sampling points across Ostrava, 59 of them for July to October 2026. Values run from 0.549 mmol/L at Bartovice to 2.16 mmol/L at Stará Bělá, and the city median is 0.872 mmol/L, about 87 mg/L CaCO₃. That makes most of the city soft, with a few harder outer districts. The median is ours, computed from the printed point values. Hardness at your tap depends on the nearest sampling point.
Czech suppliers report "Vápník a hořčík" in mmol/L; the recommended range is 2–3.5 mmol/L.
Water data
| Total hardness | 0.87 mmol/L |
|---|---|
| Utility | Ostravské vodárny a kanalizace, a.s. (OVaK) |
How Ostrava compares
- Tap water in Ostrava is 27 % softer than the median of the 1516 cities we track in Czechia (1.2 mmol/L).
- By hardness it ranks 960 of 1516 in Czechia (1 = hardest); 37 % of these cities have softer water.
Ranking of the hardest and softest water in Czechia →
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 Ostrava
| 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 Ostrava water hard or soft?
It is moderately hard: 87 mg/L as CaCO₃ (5.1 gpg, 4.9 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Ostrava safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Czech suppliers report "Vápník a hořčík" in mmol/L; the recommended range is 2–3.5 mmol/L.
How many grains per gallon is Ostrava water?
5.1 gpg, equal to 4.9 °dH, 8.7 °fH or 87 mg/L calcium carbonate.
What dishwasher salt setting should I use in Ostrava?
For 87 mg/L (4.9 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Ostrava?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: OVaK, Ostravské vodárny a kanalizace, a.s. (2026-10). Method: own measurement. OVaK, Ostravské vodárny a kanalizace, a.s. · Outdated figure? Tell us