Drinking Water in Cologne – a Clear Matter?

By Christian KäserMay 14, 2024

186,000 cubic meters – that's the amount of drinking water the RheinEnergie waterworks supply to the households and businesses of Cologne every day. Whether for drinking, cooking, washing, or flushing – water is indispensable and an integral part of everyday life. In Germany, drinking water is also one of the most rigorously tested food products. But where exactly does Cologne's drinking water come from, and how is it treated to ensure it complies with legal regulations?

The Source at Your Doorstep: The Cologne Bay

The Cologne Bay provides excellent conditions for water extraction: a continuous groundwater flow, fed by precipitation at a rate of about one meter per day, slowly permeates the subsoil. This natural process purifies the water. Approximately two-thirds of this groundwater, along with one-third of Rhine riverbank filtrate, meet the daily needs of Cologne residents. The quality of the Rhine itself has significantly improved over the last 50 years, making disinfection at the waterworks unnecessary since 1998. To keep pollutants away from groundwater, expansive water protection areas cover over 320 square kilometers on both sides of the Rhine.

Cologne Drinking Water – One of the Most Stringently Tested Food Products

Because the Drinking Water Ordinance in Germany sets strict limits, various points must be considered in both the planning and operation of water extraction and distribution and in-house installations. This includes adhering to specific limits (e.g., for lead) and testing obligations (e.g., for Legionella). This guarantees that drinking water is colorless, odorless, tasteless, and, most importantly, not harmful to health with daily use throughout Germany. The quality of Cologne's drinking water is regularly verified in the RheinEnergie water laboratory. Detailed values for mineral content and hardness can be found on the Test Wasser website.

Hard Drinking Water – a Problem?

Cologne's drinking water falls into the hard category with a hardness level exceeding 14° German hardness. This means the water is rich in magnesium and calcium, accumulating as it flows through calcareous rock. A high mineral content in water is advantageous for humans: calcium and magnesium are crucial for tooth and bone structure. Calcium is an essential component of the skeleton and indispensable for normal blood clotting. Both substances also contribute to the smooth functioning of many metabolic processes and regulate the excitability of muscles and nerves. However, hard water can lead to lime deposits and faster corrosion in household appliances and pipes. Regular descaling and maintenance of devices are recommended.

How Does the Water Reach Your Glass?

The centralized water supply in Cologne began in 1872. Today, RheinEnergie extracts raw water in its own wells and feeds it into the city's two separate drinking water networks. In the eight waterworks in Cologne, drinking water is treated and then directed into the left and right Rhine drinking water networks. Although drinking water undergoes regular checks, property owners are responsible for the drinking water installation and, consequently, water quality from the property boundary onwards. Due to old pipes, fittings, or poorly maintained hot water heaters, germs and other harmful substances can still enter the tested Cologne tap water. If you want to ensure your drinking water is healthily safe, you can easily and freely test it, for example, through the Trinkwasser-Verband Köln.