Water hardness in Mettmann
15 °dH very hard
Tap water in Mettmann is very hard: 15 °dH (268 mg/L · 15.6 gpg · 26.8 °fH).
Source: Stadtwerke Duesseldorf Trinkwasseranalyse 2026 (Auswertung Hochbehaelter Hardt, period 01.01.2025-31.12.2025) (2025) · data checked 2026-10-23
Mettmann is supplied by Stadtwerke Düsseldorf, and the figure of 267.8 mg/L CaCO₃ comes from its 2025 evaluation of the Hardt reservoir, the same value shown for Düsseldorf. Nearby Wülfrath (146.4 mg/L) and Velbert (133.9 mg/L) are much softer in our data. Do not copy a neighbour's figure when sizing a softener.
German law (WRMG) uses 3 bands: soft < 8.4 °dH, medium 8.4–14 °dH, hard > 14 °dH.
Water data
| Total hardness | 15 °dH |
|---|---|
| Utility | Stadtwerke Duesseldorf (Wasserversorgung Duesseldorf and Mettmann) |
How Mettmann compares
- Tap water in Mettmann is 30 % harder than the median of the 809 cities we track in Germany (11.5 °dH).
- By hardness it ranks 258 of 809 in Germany (1 = hardest); 68 % of these cities have softer water.
- In Nordrhein-Westfalen it is number 26 of 153 cities; the regional median is 11.3 °dH.
- Nearest city with clearly softer water: Wülfrath, 6 km away (8.2 °dH).
- Nearest city with clearly harder water: Heiligenhaus, 8 km away (19.7 °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 Mettmann
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 15 °dH |
| AEG / Electrolux | 4 |
| Beko | 4th |
| Hoover | S2 |
| LG | H3 |
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 Mettmann water hard or soft?
It is very hard: 268 mg/L as CaCO₃ (15.6 gpg, 15 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Mettmann 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 Mettmann water?
15.6 gpg, equal to 15 °dH, 26.8 °fH or 268 mg/L calcium carbonate.
What dishwasher salt setting should I use in Mettmann?
For 268 mg/L (15 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Mettmann?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: Stadtwerke Duesseldorf Trinkwasseranalyse 2026 (Auswertung Hochbehaelter Hardt, period 01.01.2025-31.12.2025) (2025). Method: figure published by the water supplier. Stadtwerke Duesseldorf Trinkwasseranalyse 2026 (Auswertung Hochbehaelter Hardt, period 01.01.2025-31.12.2025) · Outdated figure? Tell us