Tap water quality in Cologne

The importance of water quality for health

The quality of tap water plays a key role in our health. Clean drinking water not only supplies the body with vital fluids, but also protects against pollutants such as lead, nitrate or germs, which can occur if the water quality is poor.

In Cologne, where some of the water is drawn from the Rhine, strict monitoring is essential to minimize risks. High-quality drinking water strengthens the immune system and promotes well-being - all the more reason to keep a close eye on standards.
For this reason, it is crucial to have clarity about what components are present in the water and how reliable the Tapwater actually is. Regular testing and treatment of the water plays a key role in ensuring that it meets the high legal standards and does not contain any substances that are harmful to health.¹

Origin and extraction of Cologne's drinking water

Around two thirds of Cologne's drinking water comes from groundwater and one third from bank filtrate, which is extracted in the Bay of Cologne. RheinEnergie AG, the city's main supplier, uses a steady stream of groundwater that is fed by seeping precipitation and surface water. This lies at depths of between 8 and 25 meters and flows naturally northwards in the Cologne Bay - a geological "bowl" with the Rhine as its lowest point. The bank filtrate is formed when Rhine water is filtered through the subsoil, with layers of gravel and sand acting as natural purification stages. Thanks to this process, the water arrives at the extraction wells in high quality.²

The water is extracted via ten waterworks, including Weiler, Severin, Hochkirchen and Höhenhaus, which can pump up to 30,000 cubic meters of water per day - the equivalent of around 13 full swimming pools. The raw water is collected in wells, treated in the waterworks and then fed into the separate drinking water networks on the left and right banks of the Rhine. 

Water treatment

The treatment of Cologne's drinking water is a precise process that guarantees the highest quality. As the water mainly comes from groundwater and bank filtrate from the Rhine, it already benefits from natural filtration through layers of gravel and sand. Nevertheless, it undergoes several steps at RheinEnergie AG's waterworks in order to meet the strict requirements of the Drinking Water Ordinance.³

Quality assurance

To ensure quality, RheinEnergie operates its own laboratory, which analyzes over 16,000 samples every year. Forest areas and water protection areas, such as in the north of Cologne near Weiler or in the south near Rodenkirchen, protect the springs from contamination. In exceptional cases, such as when germs are found, as in Höhenhaus in 2022, the water is also chlorinated. ^4,5

Ingredients of the tap water in Cologne

How rich in minerals is Cologne's drinking water? The Tapwater comes from groundwater and bank filtrate, but there are differences: it is harder and more calcareous on the left bank of the Rhine and somewhat softer on the right bank. What substances does it contain and how do they affect the quality? Find out everything you need to know about the composition here.⁶

Is Tapwater drinkable in Cologne?

Drinking water quality in Cologne is an important issue for residents, as water is an essential part of everyday life. Germany is considered one of the countries with the strictest controls on Tapwater, and Cologne is no exception. This section looks at the legal requirements, taste and hardness of water, as well as possible contaminants and their health effects.

Legal regulations and limit values

Cologne's drinking water is subject to the German Drinking Water Ordinance (TrinkwV), which sets strict limits for pollutants such as nitrate, lead and pesticides. RheinEnergie analyzes over 16,000 samples every year and regularly confirms that the values are adhered to. Thanks to modern treatment and natural filtering by the Cologne Bay, the water meets the legal requirements.

Taste and water hardness

The taste of Cologne's tap water is characterized by its mineral-rich composition, particularly calcium and magnesium. With a hardness of 18.6 °dH on the left bank of the Rhine and 14.2-15.2 °dH on the right bank, it is considered "hard". This can cause a slightly chalky taste, which some people find less pleasant. Nevertheless, the hardness is harmless to health and provides valuable minerals.

Possible contamination and health effects

Trotz hoher Qualität sind Verunreinigungen nicht ausgeschlossen. Spurenstoffe wie Süßstoffe (z. B. Sucralose < 0,0001 mg/L) oder Glyphosat (< 0,1 µg/L) wurden im Grundwasser nachgewiesen, liegen aber weit unter gesundheitlich relevanten Werten.

In Altbauten können alte Bleileitungen das Wasser belasten – ein Problem, das Hauseigentümer beheben müssen. Keime wie Legionellen treten selten auf, meist durch Stagnation in Hausleitungen. Solche Ausnahmen (z. B. temporäre Chlorung 2022 in Höhenhaus) zeigen, dass das Wasser versorgerseitig sicher ist, aber die Hausinstallation entscheidend bleibt.

Current cases of drinking water contamination in Cologne and the surrounding area

• 14.01.2025 - Greenpeace finds high levels of carcinogenic substance in the Rhine
  The environmental protection organization Greenpeace has found high concentrations of a hazardous substance in the Rhine. The chemical PFOS is considered carcinogenic.
• 29.04.2024 - Legionella in drinking water: tenants in Dulsberg concerned
  Tenants in Hamburg-Dulsberg are concerned about legionella in their drinking water. These pathogens can cause severe pneumonia.
• 16.11.2022 Drinking water smells of chlorine
  RheinEnergie has to chlorinate the drinking water in several districts of Cologne. The reason is so-called coliform germs.

These cases are exceptions, but they show that the quality of the house connection depends on the condition of your pipes. If you are unsure, you can use a water filter.

Measures to improve tap water in Cologne 

Use of a water filter

A water filter can individually improve your Tapwater . Activated carbon filters, such as those offered by brands like Brita or ALB Filter, reduce limescale, traces of chlorine (e.g. after temporary chlorination) and micropollutants such as PFAS, microplastics or pesticide residues that may be present in traces.

In old buildings, special filters also help against lead from old pipes, which can exceed the legal limits (0.01 mg/L). The result: softer water with a more neutral taste, which is easy on appliances such as kettles and enhances the drinking experience.

Although RheinEnergie emphasizes that filters are not absolutely necessary, it is still a popular option for many Cologne residents.

Further options for improving the water quality

In addition to filters, there are other approaches to improving

modernizing domestic installations:
In older buildings, lead pipes should be replaced as they can affect the water quality right up to the tap. The City of Cologne and RheinEnergie provide support with advice and funding programs.

Regular flushing:
Stagnant water in pipes can promote germs such as legionella. Before drinking, you should let the water run briefly, especially after a long absence.

Nature conservation in water catchment areas:
RheinEnergie safeguards quality in the long term through conservation areas such as those in Weiler or Rodenkirchen, which minimize contamination from agriculture or industry. Citizens can support this indirectly by acting in an environmentally conscious manner.

Conclusion

Cologne's Tapwater is safe, high quality and drinkable. Thanks to strict controls by RheinEnergie and the Drinking Water Ordinance, it meets all standards. It is rich in minerals such as calcium and magnesium, although it is harder on the left bank of the Rhine than on the right, which can lead to calcification of household appliances. Impurities such as trace substances or lead in old buildings are rare but do occur. Sensitive people such as pregnant women or small children can additionally protect themselves with water filters. The water should be allowed to run for a short time during longer periods.