Nitrate in drinking water: limit value, contamination and filters

Nitrate has the formula NO₃⁻, and the limit value in German drinking water is 50 mg/l. Of 18,843 nitrate measurements by suppliers subject to reporting requirements, exactly 6 exceeded it in 2022, a compliance rate of 99.97%. The contamination sits one stage earlier. In groundwater, around 15.7% of monitoring sites exceeded the value of 50 mg/l in 2024. Under agricultural use, the figure was 25.6%.

This guide draws a clear line between groundwater and drinking water. It explains where the nitrate comes from, which figures the Nitratbericht 2024 (German Nitrate Report 2024) gives and which 2 health risks are scientifically established. At the end, it shows which 3 methods retain nitrate and which 3 let it pass through.

The Trinkwasserverordnung (German Drinking Water Ordinance) sets the limit value for nitrate at 50 mg/l, as set out in Annex 2, Part I. The value applies to all ages and is based on the EU Drinking Water Directive 2020/2184. For nitrite, the limit is 0.50 mg/l, and 0.10 mg/l at the outlet of the waterworks.

The structure of Annex 2 reveals more than it seems at first glance. Part I lists substances whose concentration usually remains the same throughout the distribution network. Nitrate is listed there, while lead and copper are listed in Part II. This means that your supplier's value also applies to your tap.

If both substances occur at the same time, a sum formula applies. The nitrate concentration divided by 50 plus the nitrite concentration divided by 3 must not exceed 1. At 45 mg/l of nitrate, this means that 0.30 mg/l of nitrite remains permissible instead of the otherwise permitted 0.50 mg/l.

A stricter standard applies to packaged water labelled as suitable for preparing infant food. For such water, Annex 6 of the Mineral- und Tafelwasser-Verordnung (German Mineral and Table Water Ordinance) allows 10 mg/l of nitrate and 0.02 mg/l of nitrite. In addition, there are limits of 20 mg/l for sodium and 0.7 mg/l for fluoride.

4 pathways dominate the input: fertilisation, livestock farming, wastewater and combustion. The nitrogen cycle also contributes a natural background level, which remains below 10 mg/l in unpolluted areas. Anything above that is due to human input.

When it comes to nitrate pollution, 2 separate monitoring networks are regularly confused. The distinction pulls the figures apart by around 10 percentage points.

The network of the European Environment Agency (EEA) takes measurements across all types of land use. Of 1,147 monitoring sites, exactly 15.7% were above 50 mg/l in 2024, while 47.0% remained below 10 mg/l. In 2008, 18.2% were above the limit value. The decline over 16 years therefore amounts to 2.5 percentage points.

The EU nitrate monitoring network, by contrast, is a pure pollution monitoring network. It specifically covers sites with arable land, grassland or special crops in the catchment area. For 2020 to 2022, the Nitratbericht 2024 reports more than 50 mg/l at 25.6% of monitoring sites. In the period 2016 to 2019, the figure was 26.6%.

A second value from the same evaluation shows how high the contamination is at the affected sites. On average, the monitoring sites above the limit value show 98.0 mg/l, almost double. For 2016 to 2019, the average was 96.2 mg/l, and for 2012 to 2015 it was 99.4 mg/l.

The trend is slowly pointing downwards. The proportion of slightly polluted monitoring sites with up to 25 mg/l rose from 49.0% to 51.2%. The average concentration fell at 34.4% of monitoring sites and rose at 23.0%.

A third value applies at the level of groundwater bodies. 22.2% of Germany's 1,291 groundwater bodies are considered to be in poor chemical status because of nitrate. A groundwater body is a volume of water underground that is managed as a unit. The classification obliges the authorities to draw up programmes of measures and says little about the level at your own tap.

According to the Nitratbericht 2024, regions with high livestock density and areas with intensive vegetable growing are more heavily polluted than average. The regional differences are considerable. A national average is therefore of little use for your own situation, and the figure from your supplier's report beats any map.

Around 70% of Germany's drinking water comes from groundwater. Between raw water and tap lie treatment, blending and continuous monitoring. For the nitrate parameter, this interplay works measurably well.

The report on the quality of drinking water in Germany for 2020 to 2022 provides the figures. In 2022, 2,378 suppliers subject to reporting requirements tested 18,843 samples for nitrate, and 6 measurements exceeded the limit value. The compliance rate is therefore 99.97%. Across all 3 reporting years, exceedances ranged between 0.01% and 0.04% of tests.

To put this into context, the Umweltbundesamt (German Environment Agency) states in its FAQ, as of 24 February 2026, that drinking water is the most closely monitored foodstuff and that its quality is consistently very good to good. The same applies, it says, to the virtually nationwide compliance with the nitrate limit value.

Suppliers achieve this in 3 ways. They blend contaminated raw water with less contaminated raw water. They relocate or deepen wells. And they conclude cooperation agreements with farmers in the catchment area. Technical nitrate removal at the waterworks is the most expensive option and remains the exception.

This effort costs money. A study by the Umweltbundesamt puts possible price increases in heavily polluted areas at 32 to 45%. Nitrate pollution is thus paid for through the water bill, even where the limit value is reliably met.

No fewer than 3 sets of regulations interlock, and 2 rulings from October 2025 have shaken them. The EU Nitrates Directive of 1991 (Directive 91/676/EEC) obliges member states to adopt action programmes against nitrate from agriculture. The EU Drinking Water Directive 2020/2184 sets the limit value of 50 mg/l. The German Trinkwasserverordnung (Drinking Water Ordinance) and the Grundwasserverordnung (Groundwater Ordinance) transpose it into national law.

Implementation was disputed for a long time. In 2013, the European Commission opened infringement proceedings because the German action programme fell short of the Nitrates Directive. Germany amended its fertiliser legislation in 2017 and revised the Düngeverordnung (Fertiliser Ordinance) again in 2020. The core of the reform was the designation of nitrate-polluted areas, commonly referred to as red areas. Since then, fertilisation there has had to be reduced by 20%. On 1 June 2023, the Commission closed the proceedings.

3 routes lead to a result, with very different levels of effort. The published value from your supplier costs 0 euros. Test strips cost a few euros, a laboratory analysis around 30 to 60 euros. For tap water from the public network, the first route is generally sufficient.

Your supplier's value. Every supplier discloses its analysis values, usually on its website or with the bill. The value applies to the water fed into the network. For nitrate, it also applies to your tap. Annex 2, Part I lists precisely those substances whose concentration remains the same in the network. Lead and copper would be a different matter, because both only dissolve in the domestic plumbing.

Test strips for home use. They cost a few euros and show an approximate value by means of a colour reaction. That is enough for a rough assessment. When it comes to whether a value is just below or just above 50 mg/l, their accuracy is too low.

Laboratory analysis. An accredited laboratory determines nitrate by ion chromatography in accordance with DIN EN ISO 10304-1, with a lower application limit of 0.1 mg/l. Alternatively, photometric determination is carried out in accordance with DIN 38405-9. The guide on water quality shows which other methods a drinking water analysis includes. For well owners and households with infants, the laboratory route is the right choice.

For a private well, 1 test per year is recommended, more often if there is known prior contamination. It makes sense to take a sample in spring after the fertilising season, because values are then at their highest.

The effect appears with a delay. Depending on soil type and depth to groundwater, 5 to 50 years pass between a change in fertilisation practice and a measurable effect in groundwater. The decline from 26.6% to 25.6% between the two reporting periods reflects precisely this inertia.

In its position paper of 21 January 2026, the Deutscher Verein des Gas- und Wasserfaches (DVGW, German Technical and Scientific Association for Gas and Water) calls for farm-level nutrient balances as the basis for lean impact monitoring. From the suppliers' point of view, only such a balance provides the basis for distinguishing farms that operate in an environmentally sound way from those causing the pollution.