Cologne draws groundwater from the Cologne Bight (Kölner Bucht), part of which is bank filtrate of the Rhine. It is hard, well treated and slightly different in the districts on the left bank of the Rhine than on the right bank.
Water hardness
16.5 °dHhardA lot of calcium and magnesium: good for the body, a nuisance for appliances. Descale regularly and use more detergent. Descale: every 4 weeks.
Aquaviana’s advice
- Hardness is 14 to 19 °dH depending on the waterworks; RheinEnergie shows it by postcode.
- Limescale: descale every four to six weeks.
- Nitrate is higher than in Alpine cities because of farming in the Cologne Bight, but safely below the limit.
Where the water comes from
RheinEnergie operates waterworks in Hochkirchen, Weiler, Severin, Westhoven and Höhenhaus. They draw groundwater from the gravel and sand layers of the Cologne Bight, part of it bank filtrate of the Rhine, which is cleaned as it seeps through. Treatment removes iron and manganese, and at some sites the water is post-filtered with activated carbon. Chlorine is used only when needed.
Hardness and taste
Cologne water is hard, mostly 14 to 19 °dH (about 250 to 340 mg/l CaCO3), tending to be somewhat harder on the left bank of the Rhine. It tastes full and slightly mineral. Calcium is 90 to 110 mg/l and nitrate 10 to 25 mg/l, which is a good value for a region with intensive farming and far below the limit of 50.
What that means day to day
Limescale is present but manageable. For coffee and tea, a jug filter makes the water softer and rounds off the taste. If you buy bottled water, you can switch without worry: Cologne water is tested more often than any mineral water. In the city’s many older buildings, it is worth taking a look at the pipes.
Try it out
Hardness converterConvert °dH, °fH, °e, mmol/l and ppm into one another and read off the hardness range and descaling interval.Tap water checkEight questions about your home, pipes and region, an assessment with a traffic light and next steps.Share
