When I first started out as a home barista, I was so enthusiastic about preparing coffee with a portafilter machine and about the topic of coffee that I had neglected one of the most important variables: water!
By this I don't just mean the use of decalcified water, but rather how the water defines the taste of the coffee. Whether your coffee tastes flat, bitter or sour does not just depend on how you prepare it. This is actually logical when you consider that an espresso can have a water content of around 90%. The water content of filter coffee is even around 98%!
What does good water mean?
If the coffee machine is protected from excessive limescale and corrosion and the optimal coffee taste develops, then we are talking about good water.
You can achieve this if your water has the following properties and values:
In general:
The water should be clean, fresh, colorless and odorless (absolutely free of chlorine).
The pH value should be between 6-8.
For espresso:
The total hardness should be between 4 and 7 °dH (approx. 70 and 125 ppm CaCO3)
The alkalinity should be between 2 and 4 °dH (approx. 35 and 70 ppm CaCO3)
The coffee machine should primarily be protected against limescale (too hard water) and corrosion (too soft water...low pH value?)
The following applies to filters*:
The total hardness should be between 2 and 4 °dH (approx. 35 and 70 ppm CaCO3)
The alkalinity should be between 1 and 2 °dH (approx. 18 and 35 ppm CaCO3)
Here the focus is on the development of aromas, so softer water with a low mineral content can be chosen.
*I am referring to light roasted specialty coffees.
How do I find out if water is suitable for making coffee?
You can generally find out the hardness of your water at home using test strips, titration drops or a TDS meter. The accuracy of the test result depends directly on the method used.
Test strips offer a quick solution: simply dip a test strip briefly into the water sample and wait until the fields change color. The result can then be compared with the attached table to read the water hardness range.
You can work more precisely with the titration drops . There is a liquid solution for the total hardness (magnesium and calcium) and one for the carbonate hardness (alkalinity, hydrogen carbonate). The hardness is measured by adding a colored solution to a 5 ml water sample. The number of drops until the color of the water changes from red to green, for example, gives the degree of German hardness. This method is called the titration principle.
By the way, when comparing the total hardness with the carbonate hardness, the rule of thumb is that the carbonate hardness must never be higher than the total hardness. This is particularly dangerous with desalination systems that use sodium to decalcify very hard water. Not only can the coffee machine be damaged, but the coffee will also not taste good (salty, musty). In such a case, you can use tap water directly from the garden hose and simply decalcify it with a filter cartridge. It is therefore highly advisable to check the water in such cases with titration drops.
The quickest way to get an indication of water quality is to use a TDS meter . TDS stands for Total Dissolved Solids. This measuring tool indicates the sum of solids dissolved in the water, including salts, metals and minerals. The total is expressed in ppm (parts per million). The TDS meter therefore measures the conductivity of the water, since ions are conductive. Calcium and magnesium, as well as other ions such as potassium and sodium, are counted. The value displayed in ppm can then be converted to German degrees of hardness (°dH) using a converter. However, it is important to note that this is only a rough guide and does not provide a detailed analysis of the water composition.
Conclusion: I prefer titration drops to determine the degree of hardness because they are more accurate and can also determine the carbonate hardness. On the other hand, my faithful and daily companion is my TDS meter. I use it every time to check the water before it goes into the water tank of the machine or the kettle.
What options are available for home?
The use of filter cartridges
Filter cartridges can be used as external table water filters or, in some coffee machines, they are even already integrated into the water tank. Filter cartridges not only make tap water softer, but also filter out impurities and neutralize the taste. If the tap water is very hard, from around 16 °dH, I recommend filtering in at least two passes. This means that, based on experience and with new filter cartridges, the total hardness of the tap water is reduced by around half. With a second filtering, the total hardness can be reduced by a further 10-15%. I always check the result with a TDS meter.
Filter cartridges should be replaced at least every 4 weeks for hygienic reasons due to the formation of germs.
The use of built-in filters
Built-in filter solutions from Brita or BWT are installed permanently below the tap. These filters work on the principle of reverse osmosis. The tap water is pressed through various fine-pored filters using tap pressure. The so-called bypass is used to set the desired hardness level: part of the water is filtered and cleaned, while the bypass water is only cleaned. Both water streams mix and, depending on the bypass setting, the desired hardness level is achieved. The bypass setting can be easily carried out according to a table.
Depending on the tap water quality, such filters can be used for between 6 and 12 months . Simply follow the manufacturer's specific recommendations for replacing the filters.
The use of mineral water
Mineral water offers full transparency, as all the mineral ingredients it contains are declared on the label. Only the total hardness needs to be calculated, but you simply need to enter the calcium and magnesium values in the fischerlexikon.eu converter. The alkalinity is given as HCO3 and is considered an acid buffer. This can also be converted to dH and is then considered carbonate hardness.
Back to mineral water: I use Acqua Panna for espresso. Volvic is also often recommended. One important point is the chloride in the water. Too much of it leads to corrosion problems. The SCA recommends a maximum of 30 mg per litre. Acqua Panna has 9 mg and Volvic has 15 mg.
For filter coffee, I like to use Europe's lightest water, "Lauretana" from Italy. I use Lauretana either pure or together with water that contains more minerals (for example Rocchetta or Evian) or with mineral drip solutions from Lotus Water. As already mentioned, I always measure the end result with a TDS meter (on average 60 ppm).
Ready-made mineral solutions for mixing yourself
For the nerds, perfectionists and control freaks among us, there are ready-made and optimally balanced mineral solutions (Third Wave Water, Aquacode) that you simply mix with distilled water (as just mentioned, Lauretana can also be used as a base).
As a rule, one bag is enough for 5 liters of water. If you want, you can also dose it yourself and experiment.
With the TDS meter you can keep an eye on the ppm value, which can easily be 145 ppm, for example, which is more than stated above. But that doesn't matter with ready-made solutions, as these are perfectly tailored to your coffee. The 145 ppm are just the measured particles in the water, and depending on the dosage, these can be the maximum value (1 bag in 5 liters) or even lower if you increase the amount of water in proportion.
Minerals to mix yourself
Lotus Water goes one step further and offers the possibility of mixing your own individual water. You can play around with the minerals magnesium, calcium, sodium and potassium and experience different flavor facets from a coffee. Recipes are suggested on the official Lotus Water website.
Therefore, ready-made mineral solutions and minerals for self-mixing are considered more environmentally friendly solutions, as they produce much less waste compared to filter and bottled solutions.
Conclusion
Making coffee can be a science in itself. As you've probably figured out, the topic of water is very complex and can be explored in more depth if you want to. For example, you can try an experiment: make a coffee once with tap water and once with "good" water. Can you taste the difference?
If this topic is new to you and you were able to pick up a few tips and terms and no longer use tap water or any mineral water, then I have already achieved a lot and so have you. I wish you more enjoyable coffee and more longevity for your equipment.
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