Water hardness in Černý Dub
1.2 mmol/L hard
Tap water in Černý Dub is hard: 1.2 mmol/L (120 mg/L · 7 gpg · 6.7 °dH).
Source: ČEVAK a.s. (Veolia), Moje obec – kvalita pitné vody (2026) · data checked 2026-10-21
ČEVAK reports 120.1 mg/L as CaCO₃ for Černý Dub in Jihočeský kraj (2026), which is hard. The same value appears for several other villages in the ČEVAK data, but the utility page does not explain why. Limescale on kettles and taps is likely, and regular descaling helps.
Czech suppliers report "Vápník a hořčík" in mmol/L; the recommended range is 2–3.5 mmol/L.
Water data
| Total hardness | 1.2 mmol/L |
|---|---|
| Calcium (mg/L) | 40 |
| Magnesium (mg/L) | 5 |
| Utility | ČEVAK a.s. |
How Černý Dub compares
- Tap water in Černý Dub is close to the median of the 1516 cities we track in Czechia (1.2 mmol/L).
- By hardness it ranks 603 of 1516 in Czechia (1 = hardest); 47 % of these cities have softer water.
- In Jihočeský kraj it is number 78 of 505 cities; the regional median is 1.2 mmol/L.
- Nearest city with clearly softer water: Koroseky, 2 km away (0.33 mmol/L).
- Nearest city with clearly harder water: Srnín, 11 km away (1.94 mmol/L).
Ranking of the hardest and softest water in Czechia →
What it means at home
- Fast scale on taps, shower screens and kettle; white spots on glassware.
- Water heater: efficiency loss and element failures within years if unprotected.
- Dry skin and dull hair after showering are common.
- Softener recommended; jug or reverse osmosis for drinking.
How much salt will you use for softening?
Recommended, especially with a heater or boiler: scale cuts efficiency and shortens its life.
Descale a coffee machine or kettle about every 2 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Černý Dub
| Brand | Setting for this water |
|---|---|
| Bosch | H01 |
| Miele | 7 °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 Černý Dub water hard or soft?
It is hard: 120 mg/L as CaCO₃ (7 gpg, 6.7 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Černý Dub 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 Černý Dub water?
7 gpg, equal to 6.7 °dH, 12 °fH or 120 mg/L calcium carbonate.
What dishwasher salt setting should I use in Černý Dub?
For 120 mg/L (6.7 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Černý Dub?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
Source
Source: ČEVAK a.s. (Veolia), Moje obec – kvalita pitné vody (2026). Method: figure published by the water supplier. ČEVAK a.s. (Veolia), Moje obec – kvalita pitné vody · Outdated figure? Tell us