Water hardness in Duisburg
12.5 °dH very hard
Tap water in Duisburg is very hard: 12.5 °dH (223 mg/L · 13 gpg · 22.3 °fH).
Source: Stadtwerke Duisburg (SWDU) - Chemisch-physikalische Wasseranalyse, Jahresmittelwerte 2025 (2025) · data checked 2026-10-19
Range across supply zones: 179–357 mg/L.
4 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| °dH | mg/L | ||
|---|---|---|---|
| Baerl | 13 | 232 | very hard |
| Homberg | 12 | 214 | very hard |
| Nord (without Homberg and Baerl) | 11 | 196 | very hard |
| Süd (Versorgungsbereich 1, südlich der Ruhr einschl. Rheinhausen) | 18 | 321 | very hard |
Stadtwerke Duisburg publishes 2025 annual means for four supply areas: Süd, Nord, Baerl and Homberg. The median is 223.1 mg/L CaCO₃ and the range is 178.5 to 357.0 mg/L, because the southern area is much harder than the northern one. Your supply area depends on your address, so check the SWDU area map first.
German law (WRMG) uses 3 bands: soft < 8.4 °dH, medium 8.4–14 °dH, hard > 14 °dH.
Water data
| Total hardness | 12.5 °dH |
|---|---|
| Utility | Stadtwerke Duisburg (SWDU) |
How Duisburg compares
- Tap water in Duisburg is 9 % harder than the median of the 809 cities we track in Germany (11.5 °dH).
- By hardness it ranks 364 of 809 in Germany (1 = hardest); 55 % of these cities have softer water.
- In Nordrhein-Westfalen it is number 60 of 153 cities; the regional median is 11.3 °dH.
- Nearest city with clearly softer water: Mülheim an der Ruhr, 8 km away (8.3 °dH).
- Nearest city with clearly harder water: Ratingen, 16 km away (19.1 °dH).
Ranking of the hardest and softest water in Germany →
What it means at home
- Severe scale: heater elements and washing-machine heaters fail early.
- Detergent use is very high; taps and screens coat within days.
- Dishwasher at maximum salt setting.
- An ion-exchange softener is practically essential; RO for drinking water.
How much salt will you use for softening?
Yes. At this hardness a softener pays for itself through appliance life and detergent.
Descale a coffee machine or kettle about every 1 months (typical manufacturer guidance for this hardness).
Estimates for planning, not a quote. Check your appliance manual for exact settings.
Dishwasher setting in Duisburg
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 12 °dH |
| AEG / Electrolux | 3 |
| Beko | 3rd |
| Hoover | S2 |
| 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 Duisburg water hard or soft?
It is very hard: 223 mg/L as CaCO₃ (13 gpg, 12.5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Duisburg 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 Duisburg water?
13 gpg, equal to 12.5 °dH, 22.3 °fH or 223 mg/L calcium carbonate.
What dishwasher salt setting should I use in Duisburg?
For 223 mg/L (12.5 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Duisburg?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: Stadtwerke Duisburg (SWDU) - Chemisch-physikalische Wasseranalyse, Jahresmittelwerte 2025 (2025). Method: figure published by the water supplier. Stadtwerke Duisburg (SWDU) - Chemisch-physikalische Wasseranalyse, Jahresmittelwerte 2025 · Outdated figure? Tell us