Coffee water - what does water have to be like for perfect coffee?

Water is the basis of almost everything: 70 percent of the earth is covered with water, the human body consists of up to 65 percent water and our coffee even consists of up to 98 percent coffee water . You see - water is important! Especially for our coffee. And right from the start... not all water is good for the taste. This is mainly due to the hardness - i.e. the mineral ingredients such as magnesium and calcium, which have a massive effect on the taste of the end product. And one more thing: In the DACH region you can basically always brew a "relatively" good coffee with normal tap water. But we'll look at all of this in more detail now.

Coffee water hardness wild coffee roastery spring water

Coffee water - What can be in water

In its purest state, water is H₂O, as we all know from chemistry class. But pure water is not found anywhere on our planet. It always contains minerals and trace elements. And in the worst case, it also contains harmful substances such as bacteria, chlorine, heavy metals, microplastics, pesticides and more. Important components for the quality of drinking water, such as that which comes out of our taps, can also be found at the World Health Organization. The important factors include limescale, discoloration, pH value, microorganisms, etc. All of these ingredients can have a positive or negative effect on our health and the taste of our brewed coffee.

Coffee water – what is good for your coffee?

The Specialty Coffee Association, or SCA for short , has published guidelines and standards for coffee water, specifically for the preparation of specialty coffee. The following points must be met.

  • Clean, fresh water without odor (e.g. chlorine)
  • Clear color
  • The amount of dissolved particles should not exceed 150 mg/l , but should be between 75 and 250 mg/l
  • The alkalinity of the water should be between 40 and 70 ppm (parts per million) CaCO3, calcium carbonate
  • The water hardness must be between 50 and 175 ppm CaCO3
  • The pH value should be 7 , but at least between 6 and 8


Yes, that is very scientific. But these standards are not compulsory; they represent the best case scenario and apply, for example, under competition conditions. At home, clean, clear water without the smell of chlorine is basically sufficient. In the DACH region, for example, this is always tap water.

Coffee water - magnesium and calcium

Minerals such as magnesium, calcium and sodium are not only important for us humans, they also play an important role in brewing coffee. If you get things wrong and don't balance the composition of these components correctly, the coffee can quickly taste too weak, flat, dull, sour, chalky or too strong. Our barista champion and person responsible for Wildkaffee Austria, Martin Wölfl, has experimented a lot with water, for example. It turned out that magnesium has a positive effect on the coffee water and the sweetness of the coffee. Professionals don't bother with tap water anyway, and rarely with filtered water either. They mix it themselves. So distilled water and then add the minerals that make the coffee good.

Coffee water –
Filter or mix

As already mentioned, we can always brew good coffee with tap water - at least here in the DACH region. You can go one step further by filtering your tap water. It's up to you which filter method you use; there are everything on the market, from a simple Brita filter to an osmosis system. If you want to do it like the pros, you don't filter, you mix. So you take distilled water and add the substances you need for perfect coffee water. For example , the company Third Wave Water offers pre-mixed mineral packets . If you pour one of these packets into a gallon of distilled water (just under 3.8 liters), you get coffee water that meets SCA standards. Many resellers now offer these packets in Germany.

Coffee water hardness wild coffee roasting minerals

Coffee water – dangers

But your coffee water can also be dangerous. For you, your coffee and your equipment. Limescale-containing water can lead to calcification of machines. This is particularly bad for fully automatic, portafilter and other coffee machines. Very hard water - i.e. with a high mineral content - promotes corrosion inside machines. And demineralized water - i.e. with a low hardness - leads to limescale build-up. So it is better to pay attention to what kind of coffee water goes into the machine. Apart from that , water can also contain bacteria, chlorine, heavy metals and other harmful substances. But that only happens in countries where you shouldn't drink the tap water. Here it is worth using still bottled mineral water to have good coffee water.

Coffee water-wild coffee-roastery-lime

Coffee water from the tap

You can use it safely for your coffee - at least in the DACH region, but also in many other countries. However, not all tap water is the same as good water for coffee. In Germany alone we have massive differences in hardness. The same applies within Austria and Switzerland. In Germany and Austria, water is classified with dH, German hardness, while in Switzerland people also like to use the French hardness, fH. Both hardnesses represent the content of calcium carbonate, CaCO3, and thus the lime content in the water in degrees.

1 °dH = very soft water = 17.86 mg/l CaCO3 = 1.79 °fH

At 0 to 7 degrees German hardness you have soft water, from 8 to 14 it is medium hard water and from 14 to 21 degrees it is hard water.

Coffee water – alkalinity and total hardness

So for coffee water we need an alkalinity of between 1 and 2 degrees dH and a hardness of 2 to 3 degrees . For espresso it looks like this: alkalinity between 2 and 4 degrees and total hardness between 3 and 6 degrees dH . Water hardness is now also given in three ranges 1 to 3, where 1 is soft and 3 is hard. For coffee water you should ideally be in range 1, range 2 is also fine. To find out whether tap water, for example, is suitable, you can get test strips or testing devices. These measure the alkalinity, sometimes also called carbon hardness, the degree of hardness and often also the pH value. If the water coming out of the tap is not suitable, so-called table filters or fixed filter systems can help, or you can mix purchased mineral water and tap water. The options are manifold.

Coffee water hardness wild coffee roastery Germany
Coffee water hardness wild coffee roastery Switzerland

Coffee water – water without anything

Wouldn't it be easier to just use distilled water? No, because without minerals and the like the coffee wouldn't taste good. After all, magnesium, sodium and calcium are salts and, for example, unsalted food is not as good as one that is optimally salted.

Coffee water –
by regions

German hardness is also having a major impact in Germany, unlike in Austria and Switzerland. According to a hardness map from the Federal Institute for Geosciences and Natural Resources, we have hard to very hard water in many areas. In Munich, for example, the water comes out of the tap at 13 to 19 °dH , which is medium to hard. In Vienna, on the other hand, the water comes out of the tap at just 8-9 °dH , which is in the lower middle range. Zurich has more "soft" to medium water hardness at 7 to 10 °dH . There are huge regional differences in each of the countries in the DACH region. Everything from soft to hard water is available. But fundamentally: anyone can make good coffee with tap water, perhaps run through a filter cartridge.

Coffee water – health

For all of you who are worried about too much lime etc. in the water. The lime in the water is not harmful to humans . We actually need magnesium, calcium and sodium, and whatever is present in excess in the water we simply excrete.


Coffee water – Conclusion

Water makes up 98 percent of your coffee, and a little less in milky coffee drinks. The quality of your water is therefore extremely important. The average coffee drinker can basically use our tap water . It would be better to filter the water again, as we have relatively hard water, especially in the south of Germany. If you want to do it professionally, you need a really good filter system or you can mix the water yourself from minerals and distilled water.