Water is rather important for coffee. After all, coffee consists of 98 percent water. Water must be clean, free from heavy metals and chloride and have a limited hardness.
At home I make my coffee manually. I filter the tap water with ZeroWater. At the office I filter with a reverse osmose installation. A former employee told me about the ZeroWater filters. I was very satisfied with the first results. I use it to first filter the tap water to a tds of 0, so 0 ppm. Then I add tap water to gradually increase the number of ppm to a level that is perfect for the type of coffee I want to make. Currently I am working on a coffee that ideally must be consumed with water with 75 ppm. So I first filter the tap water with ZeroWater to 0 ppm and then I add tap water till I have reached 75 ppm.
The cleaner the coffee, the cleaner the water has to be. But if the water is less clean you need heavier water. To stick to the terms of tds you could state that clean coffee must be made with water with a tds of 0, but this applies for the best coffee in the world and this concerns 1 permille of the total production worldwide. Most coffee is not clean and is ideally consumed with water with a tds of 50-125 ppm.
The recipe of a good coffee firstly depends on the feeling of the mouth; the harder and therefore the fuller the water, the fuller the feeling of the mouth. The extraction grade is also important for the recipe. How much coffee do you extract from the beans? Minerals can help with this, especially magnesium and sodium bicarbonate.
To make the perfect coffee I first mix some tap water with water filtered by ZeroWater to get the right ppm and then I possibly also add magnesium and sodium bicarbonate to get the right extraction grade of the coffee. This sounds rather a lot of work for a nice cup of coffee but if you know that a kilo of good coffee costs between 100 and 150 euro at an auction you want to make the coffee as well as possible.
I continue to use ZeroWater, because apart from the fact that the water is filtered to 0 ppm, the water also stays the same in terms of ph value after it has been filtered. The water of many other filter systems acidifies and that affects the taste.