Water hardness in Ishøj
21.5 °dH very hard
Tap water in Ishøj is very hard: 21.5 °dH (384 mg/L · 22.4 gpg · 38.4 °fH).
Source: GEUS, Drikkevandets hårdhed i Danmark (Jupiter database), CC BY 4.0 (2023) · data checked 2026-10-19
Range across supply zones: 357–391 mg/L.
All of Denmark's tap water is groundwater, and around Copenhagen the wells draw on limestone and chalk aquifers beneath glacial clay. The GEUS-reported hardness is 383.7 mg/L CaCO₃, with values from 357.0 to 390.9 mg/L depending on the street. At this hardness scale forms quickly on heating elements and fittings, so a softener or a strict descaling routine is worth considering.
Danish waterworks report hardness in °dH; GEUS classes: soft < 8, medium hard 8–12, fairly hard 12–18, hard 18–30, very hard > 30 °dH. Most Danish tap water is groundwater and hard.
Water data
| Total hardness | 21.5 °dH |
|---|
How Ishøj compares
- Tap water in Ishøj is 44 % harder than the median of the 388 cities we track in Denmark (14.9 °dH).
- By hardness it ranks 15 of 388 in Denmark (1 = hardest); 96 % of these cities have softer water.
- In Capital Region it is number 11 of 75 cities; the regional median is 18.8 °dH.
- Nearest city with clearly softer water: Brøndbyvester, 5 km away (16.6 °dH).
- Nearest city with clearly harder water: Rudkøbing, 129 km away (27.9 °dH).
Ranking of the hardest and softest water in Denmark →
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 Ishøj
| Brand | Setting for this water |
|---|---|
| Bosch | H06 |
| Miele | 21 °dH |
| AEG / Electrolux | 5 |
| Beko | 6th |
| Hoover | S3 |
| LG | H4 |
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 Ishøj water hard or soft?
It is very hard: 384 mg/L as CaCO₃ (22.4 gpg, 21.5 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Ishøj safe to drink?
Hardness is not a health issue; it is about limescale, taste and appliances. Mains water must meet national drinking-water standards. Danish waterworks report hardness in °dH; GEUS classes: soft < 8, medium hard 8–12, fairly hard 12–18, hard 18–30, very hard > 30 °dH. Most Danish tap water is groundwater and hard.
How many grains per gallon is Ishøj water?
22.4 gpg, equal to 21.5 °dH, 38.4 °fH or 384 mg/L calcium carbonate.
What dishwasher salt setting should I use in Ishøj?
For 384 mg/L (21.5 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Ishøj?
Yes, unless you are only passing through: scale damages appliances within a few years.
Source
Source: GEUS, Drikkevandets hårdhed i Danmark (Jupiter database), CC BY 4.0 (2023). Method: figure published by the water supplier. GEUS, Drikkevandets hårdhed i Danmark (Jupiter database), CC BY 4.0 · Outdated figure? Tell us