Water hardness in Iserlohn
11.8 °dH very hard
Tap water in Iserlohn is very hard: 11.8 °dH (211 mg/L · 12.3 gpg · 21.1 °fH).
Source: Stadtwerke Iserlohn Trinkwasser-Analyse (Stand Mai 2026, web page) (2026-05) · data checked 2026-10-20
Range across supply zones: 156–265 mg/L.
Stadtwerke Iserlohn lists Wasserhärte as a range, Stand May 2026, in mmol/l only, which we convert to mg/L CaCO₃: 156.1 to 265.2 mg/L. The city figure of 210.7 mg/L is the midpoint, not a measured average. The utility places the water in the hard band under the German WRMG. A neighbouring group of villages on the same page has its own value, which we do not use here.
German law (WRMG) uses 3 bands: soft < 8.4 °dH, medium 8.4–14 °dH, hard > 14 °dH.
Water data
| Total hardness | 11.8 °dH |
|---|---|
| Utility | Stadtwerke Iserlohn |
How Iserlohn compares
- Tap water in Iserlohn is close to the median of the 809 cities we track in Germany (11.5 °dH).
- By hardness it ranks 389 of 809 in Germany (1 = hardest); 52 % of these cities have softer water.
- In Nordrhein-Westfalen it is number 65 of 153 cities; the regional median is 11.3 °dH.
- Nearest city with clearly softer water: Hemer, 5 km away (6.5 °dH).
- Nearest city with clearly harder water: Heiligenhaus, 51 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 Iserlohn
| Brand | Setting for this water |
|---|---|
| Bosch | H03 |
| 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 Iserlohn water hard or soft?
It is very hard: 211 mg/L as CaCO₃ (12.3 gpg, 11.8 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Iserlohn 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 Iserlohn water?
12.3 gpg, equal to 11.8 °dH, 21.1 °fH or 211 mg/L calcium carbonate.
What dishwasher salt setting should I use in Iserlohn?
For 211 mg/L (11.8 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Iserlohn?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: Stadtwerke Iserlohn Trinkwasser-Analyse (Stand Mai 2026, web page) (2026-05). Method: computed from supplier's calcium and magnesium. Stadtwerke Iserlohn Trinkwasser-Analyse (Stand Mai 2026, web page) · Outdated figure? Tell us