I can comfortably say that you can get the best beans from the cleanest origin, roast them flawlessly, grind them perfectly, and use the most complicated brewing method, but your results will be still subpar if your water isn’t good. This comes from the fact that your coffee is 98% percent water, and tap water that most of us use for coffee brewing is not a pure ingredient, as it contains a large number of minerals and ions that will significantly influence the flavor of your coffee.
Throughout the years many coffee specialists have worked hand to hand with scientists to get to know how exactly water affects your coffee, and how and which chemical in various waters interacts with your coffee to get different results from different beans.
Coffee beans contain more than 1,000 aroma and flavor compounds which give it its distinct taste and smell that we come to know and love, and beans from different origins have different compounds that differentiate the qualities of the coffee.
Water, on the other hand, has different qualities and it can be either hard, soft or something in between. It is safe to say that softer waters are richer in sodium, and harder waters are richer in calcium and magnesium.
Some of you might think that opting for distilled water while brewing coffee might be beneficial to the whole process, but this can’t be farther from the truth. Minerals are important for the brewing process, and the right amount of minerals brings out the best flavors in coffee, and in some specific beans, hard water is beneficial.
Generally speaking, hard water is bad for your coffee, but it is not the magnesium and calcium that affects your coffee negatively, it is bicarbonate. In hard water, there are tons of minerals like I said and some of them have sticky properties, meaning that their aromas and taste stick to the major compounds of your coffee like citric acid, lactic acid, and eugenol giving your coffee a really bad taste, bitter in the majority of the cases.
Scientists have decided the best water for brewing coffee is clear, odorless, without chlorine, a little acidic and has a slight concentration of minerals, meaning that it is not distilled or pure water.
But this is really hard to achieve even if you have the best coffee maker for hard water. I would recommend you to install a water filter for your coffee machine. This will strip out the majority of the minerals and will soften your water. Installing a water filter you will also prolong the life of your coffee machine as well, besides the obvious effect of brewing perfect coffee.