Water hardness in Flensburg
7.8 °dH hard
Tap water in Flensburg is hard: 7.8 °dH (140 mg/L · 8.2 gpg · 14 °fH).
Source: Stadtwerke Flensburg – Prüfbericht UCL 06.11.2025 (2025) · data checked 2026-10-23
Range across supply zones: 129–152 mg/L.
2 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| °dH | mg/L | ||
|---|---|---|---|
| Wasserwerk Ostseebad | 8.5 | 152 | hard |
| Wasserwerk Süd | 7.2 | 129 | hard |
Stadtwerke Flensburg supplies the city from two waterworks. Ostseebad is at 151.7 mg/L CaCO₃ and Süd at 128.5 mg/L, based on a test report from November 2025. The city figure is 140.1 mg/L, in the hard category. Nearby Rendsburg (190.1 mg/L) and Kiel (300.8 mg/L) are harder.
German law (WRMG) uses 3 bands: soft < 8.4 °dH, medium 8.4–14 °dH, hard > 14 °dH.
Water data
| Total hardness | 7.8 °dH |
|---|---|
| Calcium (mg/L) | 41 |
| Magnesium (mg/L) | 6.2 |
| Utility | Stadtwerke Flensburg GmbH |
How Flensburg compares
- Tap water in Flensburg is 32 % softer than the median of the 809 cities we track in Germany (11.5 °dH).
- By hardness it ranks 577 of 809 in Germany (1 = hardest); 29 % of these cities have softer water.
- In Schleswig-Holstein it is number 23 of 26 cities; the regional median is 12 °dH.
- Nearest city with clearly softer water: Nordseeheilbad Wangerooge, 150 km away (5.7 °dH).
- Nearest city with clearly harder water: Glucksburg, 8 km away (11.1 °dH).
Ranking of the hardest and softest water in Germany →
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 Flensburg
| Brand | Setting for this water |
|---|---|
| Bosch | H01 |
| Miele | 8 °dH |
| AEG / Electrolux | 2 |
| Beko | 3rd |
| Hoover | S1 |
| LG | H2 |
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 Flensburg water hard or soft?
It is hard: 140 mg/L as CaCO₃ (8.2 gpg, 7.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Flensburg safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. German law (WRMG) uses 3 bands: soft < 8.4 °dH, medium 8.4–14 °dH, hard > 14 °dH.
How many grains per gallon is Flensburg water?
8.2 gpg, equal to 7.8 °dH, 14 °fH or 140 mg/L calcium carbonate.
What dishwasher salt setting should I use in Flensburg?
For 140 mg/L (7.8 °dH) check your manufacturer's table: level 4–5.
Do I need a water softener in Flensburg?
Recommended if you have a water heater, boiler or tankless unit: it saves repairs and detergent.
Source
Source: Stadtwerke Flensburg – Prüfbericht UCL 06.11.2025 (2025). Method: own measurement. Stadtwerke Flensburg – Prüfbericht UCL 06.11.2025 · Outdated figure? Tell us