Water hardness in Bonn
5.6 °dH moderately hard
Tap water in Bonn is moderately hard: 5.6 °dH (99 mg/L · 5.8 gpg · 9.9 °fH).
Source: SWB Energie und Wasser - Bonner Wasser ist Spitze, Wasseranalyse 2020 (2020) · data checked 2026-10-19
Range across supply zones: 88–111 mg/L.
2 supply zones — hardness varies by neighbourhood; the figure above is the median.
Hardness by district / supply zone
| °dH | mg/L | ||
|---|---|---|---|
| Versorgungsbereich I (Beuel, Bonn, Bad Godesberg) | 4.9 | 88 | moderately hard |
| Versorgungsbereich II (Hardtberg, Röttgen, Venusberg, Ippendorf, Ückesdorf) | 6.2 | 111 | moderately hard |
This figure is over 3 years old; hardness may have changed.
The only analysis we found is SWB Energie und Wasser's 2020 report, published as open data, so this page is marked stale. It gives two supply areas, with a median of 99.1 mg/L CaCO₃ and a range of 87.5 to 110.7 mg/L, which is on the soft side. Hardness may have changed since 2020, so confirm with the utility.
German law (WRMG) uses 3 bands: soft < 8.4 °dH, medium 8.4–14 °dH, hard > 14 °dH.
Water data
| Total hardness | 5.6 °dH |
|---|---|
| Utility | SWB Energie und Wasser (Bonn) |
How Bonn compares
- Tap water in Bonn is 52 % softer than the median of the 809 cities we track in Germany (11.5 °dH).
- By hardness it ranks 718 of 809 in Germany (1 = hardest); 11 % of these cities have softer water.
- In Nordrhein-Westfalen it is number 136 of 153 cities; the regional median is 11.3 °dH.
- Nearest city with clearly softer water: Leichlingen, 41 km away (4.4 °dH).
- Nearest city with clearly harder water: Bornheim (Rhein-Sieg), 4 km away (12 °dH).
Ranking of the hardest and softest water in Germany →
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 Bonn
| Brand | Setting for this water |
|---|---|
| Bosch | H00 |
| Miele | 6 °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 Bonn water hard or soft?
It is moderately hard: 99 mg/L as CaCO₃ (5.8 gpg, 5.6 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Bonn 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 Bonn water?
5.8 gpg, equal to 5.6 °dH, 9.9 °fH or 99 mg/L calcium carbonate.
What dishwasher salt setting should I use in Bonn?
For 99 mg/L (5.6 °dH) check your manufacturer's table: level 2–3.
Do I need a water softener in Bonn?
Not essential; a scale inhibitor protects the heater cheaply.
Source
Source: SWB Energie und Wasser - Bonner Wasser ist Spitze, Wasseranalyse 2020 (2020). Method: older figure, source currently unavailable. SWB Energie und Wasser - Bonner Wasser ist Spitze, Wasseranalyse 2020 · Outdated figure? Tell us