Tap water in Denmark: pure groundwater, chlorine-free in the network

Danish waterworks manage with just 2 processes. They enrich the extracted groundwater with oxygen and then pass it through sand filters. In the process, iron, manganese, ammonium, hydrogen sulphide, carbon dioxide and methane leave the water. The waterworks only go further where necessary.

In normal operation, Danish waterworks do without chlorine. This sets Denmark apart from France, where suppliers must maintain a disinfection capacity. Danish tap water therefore tastes neutral. Visitors from Germany rarely notice the difference, as German suppliers also rarely chlorinate.

Every 3 years, the EU Drinking Water Directive requires Miljøstyrelsen to take stock of water quality. The most recent report was published in January 2024, covers 2020 to 2022 and includes the approximately 200 large waterworks. The raw data comes from the national database Jupiter. The figures at the tap, totalled over all 3 years:

• Escherichia coli: 4 exceedances in 10,171 analyses, i.e. 0.04%
• Nitrate: 0 exceedances in 1,211 analyses, limit value 50 mg/l
• Total pesticides: 3 exceedances in 758 analyses, all 3 in 2020
• Coliform bacteria: 126 exceedances in 10,172 analyses, i.e. 1.2%
• Colony count at 22 degrees Celsius: 219 in 10,169 analyses, i.e. 2.2%
• Lead: 7 exceedances in 1,118 analyses, Danish limit value 5 µg/l

The most common non-compliances concern colour, turbidity, conductivity, ammonium, iron and nitrite, with rates between 1 and 7%. According to the report, such values reflect the operation of the filters and occur, for example, after the filter material has been changed.

The Geological Survey of Denmark and Greenland (GEUS) published its groundwater report on 8 December 2025, with data up to 2024. It contains the figure that is causing a stir in Denmark. In 2024, at least one pesticide residue was found in 55.1% of 2,175 waterworks abstraction points, and in 13.8% a single substance exceeded the limit value of 0.1 µg/l.

3 points put this finding into context. First, it applies to abstraction points for raw water, i.e. before treatment and distribution. Second, it counts monitoring points with at least one detection during the year, regardless of the proportion of water abstracted. Third, the value of 0.1 µg/l applies uniformly to every pesticide and every degradation product, i.e. regardless of the effect of the individual substance.

The finding varies by region. In one area of West Jutland, the abstraction points are deep, and the report records few exceedances there. For the drinking water actually supplied, the picture is different anyway. Of 758 analyses of total pesticides at the tap, 3 exceeded the limit value, all 3 in 2020. In 2021 and 2022 the figure remained at zero. The waterworks take contaminated boreholes out of service or blend their water before feeding it into the network. The guide to plant protection products in tap water describes how pesticides get into groundwater.

4 measurement levels show the same effect for nitrate. The first 3 come from the GEUS report for 2024. At shallow monitoring points under farmland, the concentration exceeded 50 mg/l in 31.1% of cases. At the deeper monitoring points, the figure was 15.8%. In the waterworks' boreholes, the proportion fell to 0.8%. At the tap, official testing found zero exceedances in 3,461 analyses.

The data covers 89 shallow monitoring points, 931 deeper ones and 1,658 boreholes. Conversely, 26.7% of the shallow monitoring points were nitrate-free, with at most 1 mg/l. For the deeper ones the figure was 41.5%, for the boreholes 81.2%. Around 17% of Denmark's land area is classified as a nitrate-sensitive abstraction area. You can read more about this in the guide to nitrate in groundwater and drinking water.

Hovedstadsområdets Forsyningsselskab (HOFOR) supplies water to Copenhagen and 7 surrounding municipalities. Twice a year, the supplier carries out extended testing and publishes the raw data. The samples from January 2026 cover 12 waterworks. In addition to chemistry and microbiology, HOFOR tests 224 parameters for foreign substances and trace metals at each waterworks. Of these, only 33 were above the limit of quantification, and all 33 remained below their limit value.

The key values across all 12 waterworks:

• Nitrate: 0.9 to 4.2 mg/l, with a limit value of 50 mg/l
• Fluoride: 0.25 to 0.87 mg/l, with a limit value of 1.5 mg/l
• Chloride: 38 to 100 mg/l, with a limit value of 250 mg/l
• Sodium: 31 to 140 mg/l, with a limit value of 175 mg/l
• Magnesium: 18 to 38 mg/l
• Nickel: up to 6.3 µg/l, with a limit value of 20 µg/l
• Uranium: up to 2 µg/l, with a limit value of 10 µg/l
• Sum of 4 per- and polyfluoroalkyl substances (PFAS): 0.00011 to 0.0014 µg/l, limit value 0.002 µg/l
• pH value: 7.28 to 8.10

Microbiologically, everything remained below the detection limit at all 12 waterworks. Coliform bacteria, Escherichia coli and intestinal enterococci were below 1 germ per 100 ml, legionella below 100 per 1,000 ml. The colony count at 22 degrees Celsius ranged from below 1 to 4 per ml; 200 are permitted.

The PFAS sum comes closest to its limit. At the Thorsbro waterworks it reached 0.0014 µg/l, i.e. 70% of the Danish limit value. The pesticide metabolite dimethylsulfamide (DMS) appeared in 9 of the 12 waterworks, at 0.019 to 0.059 µg/l, with a limit value of 0.1 µg/l. Trifluoroacetic acid was at 0.064 to 0.2 µg/l; 9 µg/l is permitted. The Danish value is ten times lower than the limit that the German Trinkwasserverordnung (Drinking Water Ordinance) sets for the same group of substances from 2028.

HOFOR states a natural hardness of 18 to over 30 degrees of German hardness for the capital region. The supplier is currently installing softening at all of its regional waterworks. The target value is 10 to 12 degrees. 4 waterworks have already been converted: Marbjerg in spring 2021, Søndersø in late summer 2022, Thorsbro in spring 2024 and Gevninge in autumn 2024.

The readings from January 2026 show the effect. Gevninge supplies 11 degrees, Marbjerg 12, Thorsbro 13 and Søndersø 14. The highest values come from Espevang with 24 and Islevbro with 23 degrees. The difference in calcium is just as marked: 42 to 46 mg/l in Gevninge and Marbjerg, 110 to 120 mg/l in Espevang, Islevbro and Slangerup.

For your stay, this means that the district of Copenhagen you are in determines how much limescale builds up in the kettle. In terms of health, hardness is irrelevant, as the guide to limescale in water explains.

In Denmark, 3 situations determine water quality, and all 3 occur downstream of the waterworks. The first is stagnation. Water that sits in a pipe for hours absorbs metals from the pipe and warms up. In the morning and after arrival, let the tap run for 1 to 2 minutes until the water flows evenly.

The second concerns the age of the household plumbing. Of 1,118 lead samples taken at the tap, 7 exceeded the Danish limit value of 5 µg/l. Lead almost always gets into the water from the pipes inside the building, less often from the network.

In the Copenhagen city area, HOFOR operates public drinking fountains on the same network. The third situation applies to hoses and tanks. If you travel by motorhome or with a water canister, empty the container before leaving and let it dry. Warm standing water in the tank is the only place in Denmark where germs can realistically grow.

Whether testing is mandatory depends on 1 criterion: whether the property is rented out. In Denmark, a rented holiday home counts as commercial use. For such properties, the municipality sets a monitoring programme specifying the frequency and scope of the analyses. The same rule applies to hotels, bed and breakfasts, campsites and food businesses. Samples may only be taken by accredited laboratories.

The situation is different for a privately used house with its own well. If a system supplies only a single private household, there is no testing requirement. For 2 to 9 households, a simplified check is required, the frequency of which is set by the municipality, usually every 5 years. The simplified check covers appearance and odour, pH value, conductivity, arsenic, nitrate, coliform bacteria, Escherichia coli and the colony count at 22 degrees Celsius.

As a tenant, you are therefore on the safe side, because your holiday home is subject to mandatory testing. If you stay with people you know in a private house with its own well, this requirement does not apply. A look at the latest analysis report will clarify the situation.

For infant food, 2 values are decisive: nitrate and microbial contamination. In Denmark, both speak in favour of tap water. Nitrate remained below the limit value of 50 mg/l in all 3,461 analyses nationwide; in Copenhagen it is between 0.9 and 4.2 mg/l. Escherichia coli occurred in 0.04% of samples.

When preparing it, the same applies as in Germany. Let the water run until it comes out cool, then boil it. Boiling targets germs from the household pipes rather than the quality of the supplier's water. If a holiday home has its own well and the analysis status is unclear, bottled water labelled as suitable for infant food remains the safer choice.

On Bornholm, the fluoride content in groundwater is above the Danish average. GEUS reported on fluoride for the first time in 2025 and gives a median of 0.43 mg/l for the aquifers on Bornholm and in limestone. Quaternary sand aquifers are at 0.18 mg/l, pre-Quaternary ones at 0.12 mg/l. Nationwide, 96 of 5,981 abstraction points were above the limit value of 1.5 mg/l on average, and the maximum value reached 4.2 mg/l. Fluoride comes from deep underground and enters the water via limestone rock.

Bornholms Energi og Forsyning operates 4 waterworks with 27 boreholes for around 12,000 households, also using aeration and sand filtration. The World Health Organization (WHO) recommends 0.5 to 1.5 mg/l of fluoride because small amounts prevent tooth decay, while more recent research from 2024 advises less than 0.3 mg/l. On holiday, this point is irrelevant, as the effects of fluoride build up over years.