Water hardness in Slagelse
16.1 °dH very hard
Tap water in Slagelse is very hard: 16.1 °dH (287 mg/L · 16.8 gpg · 28.7 °fH).
Source: GEUS, Drikkevandets hårdhed i Danmark (Jupiter database), CC BY 4.0 (2023) · data checked 2026-10-19
All of Denmark's tap water is groundwater, and on Zealand much of it comes from limestone and chalk aquifers covered by lime-rich glacial clay. The GEUS-reported hardness is 287.4 mg/L CaCO₃. 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 | 16.1 °dH |
|---|
How Slagelse compares
- Tap water in Slagelse is 8 % harder than the median of the 388 cities we track in Denmark (14.9 °dH).
- By hardness it ranks 151 of 388 in Denmark (1 = hardest); 61 % of these cities have softer water.
- In Zealand it is number 57 of 72 cities; the regional median is 18 °dH.
- Nearest city with clearly softer water: Kerteminde, 44 km away (11.5 °dH).
- Nearest city with clearly harder water: Skælskør, 17 km away (21 °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 Slagelse
| Brand | Setting for this water |
|---|---|
| Bosch | H04 |
| Miele | 16 °dH |
| AEG / Electrolux | 4 |
| Beko | 5th |
| 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 Slagelse water hard or soft?
It is very hard: 287 mg/L as CaCO₃ (16.8 gpg, 16.1 °dH). The usual bands are soft < 60, moderately hard 60–120, hard 120–180 and very hard > 180 mg/L.
Is tap water in Slagelse 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 Slagelse water?
16.8 gpg, equal to 16.1 °dH, 28.7 °fH or 287 mg/L calcium carbonate.
What dishwasher salt setting should I use in Slagelse?
For 287 mg/L (16.1 °dH) check your manufacturer's table: maximum level (5–7).
Do I need a water softener in Slagelse?
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