Coffee water – what to watch out for


Did you know that 99 % of your coffee is water? Nevertheless, water quality is often neglected when making coffee. Water that is too hard not only damages your machine, but also affects the taste of your coffee.

Minerals (lime-forming substances) make up the main component of our drinking water. The minerals consist of the total salt content, the carbonate hardness, the permanent hardness and the total hardness. Depending on rock and soil conditions, water hardness and pH value can vary greatly. Water hardness is determined by the content of calcium or magnesium ions (permanent hardness) and the carbonate hardness (temporary hardness) and is measured in °dH.

The rule: the higher the ion content, the harder the water.

If carbonate-hard water is heated, the ions settle as a grey coating (scale). Not only bacteria accumulate on these limescale deposits. These deposits impair the performance and service life of your coffee maker immensely. In addition, the coffee aromas cannot develop optimally due to the scale that forms and an unappetising film appears on the surface of your coffee. We have compiled a table with the water hardness of the largest cities. At you can also find out the water hardness of your town by entering your postcode.

Water hardness goes hand in hand with the pH value. Hard water tends to react alkaline. This is why the fruit acids found in Arabica coffees are neutralised by the alkaline character of hard water. In addition, the hardness-forming minerals develop an undesirable aftertaste. This is anything but desirable. Soft water up to 6° d, on the other hand, tends to be acidic – in extreme cases even cream curdles. Fully softened, i.e. acidic, water intensifies the acidic taste of acid-intensive green coffees, light roasts or fast-roasted coffee.

Sounds problematic – and it is!

Wasserhärte in deutschen Städten
Kaffee mit dem Kalita Wave Handfilter

Our tip for your coffee water

Ideal for preparing your coffee is water with a pH value of 7.0 and a total hardness of approx. 4 – 8°dH. You can make the pH value of soft water harder with the help of mineral granules. Since tap water in Germany is predominantly hard, we concentrate on softening methods in our tips.

For you, the simpler and cheaper solution is probably a table water filter. With Brita Professional, you would have to replace the filter regularly. But if you don’t use it too much, the running costs are still low compared to a permanently installed filter. For improving the taste and softening the water, table filters are on the whole a good and cost-effective alternative to permanently installed filters – especially for tea and coffee drinkers who boil their water before enjoying it. Filtering thus results in an almost limescale-free kettle and an unadulterated coffee taste – in other words, exactly what we want!

So funktioniert ein Tischwasserfilter

How a table filter works

A table water filter is composed of 4 different filter systems. In the pre-filtration stage, coarse particles are removed. In a further step, ions that cause limescale are replaced by sodium ions through a so-called ion exchanger and the carbonate hardness is reduced. The activated carbon filter removes unpleasant tastes and odours, such as chlorine, from the water. Last but not least, the fine filtration retains the smallest particles and heavy metals. Ionic substances such as minerals, salts and lime, however, remain in the water. A disadvantage of ion filters is that often only the filter manufacturer can regenerate the filters once they are saturated.

Contrary to a widespread misconception, table filters are by no means suitable for removing germs from the water. Quite the opposite: there is

Soft to medium hard mineral water

There are alternatives to a water filter available. We are going to present two of them: The simplest solution is to find the mineral water you like best. Shopping in the supermarket can be worth your while and solve your problem immediately. As described above, the hardness (dH/°dH) is of importance and depends on the level of magnesium and calcium especially. Try to find mineral water with magnesium and calcium levels that aren’t too far apart from each other. Let’s take a look at ten (mostly German) natural mineral waters regarding their hardness, magnesium and calcium levels:

  1. Bad Liebenwerda (2,99 dH) / Magnesium: 3,1 mg/l; Calcium: 16,2 mg/l
  2. Volvic (3,4 dH) / Magnesium: 8 mg/l; Calcium: 12 mg/l
  3. Spreequell (4-5 dH) / Magnesium: 3,3 mg/l; Calcium: 17 mg/l
  4. Fiji Water (5,98 dH) / Magnesium: 13 mg/l; Calcium: 17 mg/l
  5. RhönSprudel (10,73 dH) / Magnesium: 20,9; Calcium: 41,7 mg/l
  6. Evian (17,21 dH) / Magnesium: 26 mg/l; Calcium: 80 mg/l
  7. Adelholzener (17,44 dH) / Magnesium: 30,4 mg/l; Calcium: 92,8 mg/l
  8. Vittel (17,79 dH) / Magnesium: 20 mg/l; Calcium: 94 mg/l
  9. Gerolsteiner (30,93 dH) / Magnesium: 44 mg/l; Calcium: 125 mg/l
  10. Extaler Mineralquell (63,38 dH) / Magnesium: 59,9 mg/l; Calcium: 364 mg/l

As you can see above, out of the ten mineral waters, only three are suitable for brewing coffee because of their hardness alone. Apart from Spreequell, Volvic and the comparatively hard-to-get and expensive Fiji Water, all mineral water in our list are either too soft or too hard. Volvic and Fiji Water have the advantage of close magnesium and calcium levels. The former mineral has higher extraction power than the latter.

Rancilio Silvia

Third Wave Water

If you don’t want to constantly buy mineral water for preparing your coffee, you can try an alternative to the table filter: Third Wave Water. The US-American company made it its mission to create the perfect water for coffee. Preparing this is a little more complicated than buying mineral water or filter your water, though.

Third Wave offers three different products: One for light to medium-roasted filter coffee; one for a dark roast; and one for espressos. Let’s say you want to brew a medium-roast filter coffee: In every Third Wave Water pack for the Classic Profile are twelve sticks. In every stick is magnesium sulfate, calcium citrate, and sodium chloride – in the amount that is perfect for your filter coffee brew. You mix the contents of this stick in 1 gallon of distilled water. Stir it gently, and already you have the perfect water for your coffee according to specifications from the SCA. Now, the water has the right amount of magnesium, calcium, and the appropriate hardness.

Our tip:

Before considering the purchase of a filter, first find out the hardness of your water and whether a water filter is necessary. The easiest way to do this is to go to and find out which water company is responsible for your area. On their website you can find out the water values that are relevant for you. Or order free water hardness test strips from Brita. Within a few seconds, you can determine the hardness of your water.

Would you like to try our coffees?

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