For these tests, we used different brands of water, as well as tap water from Bordeaux. We also choose to use the new harvest Kenyan coffee, being a complex coffee not only in flavor but also in acidity, in which we can clearly evaluate which incidence water can have in its extraction (we can at the same time, remark that new harvest of Kenya brought us some incredibly bright and simply outstanding coffees ! )

Why is water important? I mean… It is just water!

When we think about coffee, water is not the first word that comes to our mind, however each cup of coffee is composed between a 98.5 and 99 % of water! Water is essential to obtain a qualitative coffee.

But water, has no odor, no color, no taste… Shouldn’t water have any incidence?

Normally yes, water has no color and no taste, but depending on where we live, the chemical composition of water changes a lot. These components of the water are able to give bad tastes that shouldn’t be in the cup! This, mainly for two reasons: 1. By their nature itself. This means that, just by being there, the components will give bad tastes, undesirables for any cup of coffee. 2. By their interaction with some components of coffee. This means that, by their interaction with some other components of coffee, they will develop bad tastes in coffee. Otherwise, this components, will not allow a good development of flavors presents in your coffee. For example, important quantities of calcium will interrupt the brightness development of your coffee.

The Belco’s Test

So, what did we do?

The Method:

Same coffee, same weight, same water quantity, same brewing method… the only difference being the water used. Blind test!

The results:

The results we obtained were astonishing. In some “coffees”, there were not very important differences, or they were almost indistinguishable… but in some others, it was almost impossible to say that we were cupping the same coffee!

The labels… or what you need to read!

We are going to show you the profiles we obtain for the same Kenyan coffee, with two different  brands of water as well as with the tap water from Bordeaux… by its composition 😉
A drink clean and round. A complete flavor development with a remarkable brightness, accentuated. Without any doubt, the best water we used for this cupping.


A drink not very clean, even tough, harsh. Undeveloped flavors compared to brand A, a short and weak brightness.


Depiste our preconceptions about Bordeaux tap water, the extraction was not as « damaged » as we could have thought. Pointless to say that the cleanness felt in coffee extracted with brand A were far from this extraction, but we had a quite straight development compared to some other waters, like brand B for example. We could explain this by different reasons, for example, the reaction that could happen between some components presents in an important quantity in some waters, with coffee components. These components might have a nutritional aim, but have certainly interfered with coffee flavor development. On the other side, even if considered as relatively hard water, Bordeaux water in its natural state has an excellent quality. The coffee obtained didn’t certainly have the roundness of coffee extracted with water brand A, but we had a good flavor development in extraction.   Some numbers you should note TDS (Total Dissolved Solids): the ideal parameter for coffee is between 125 and 175 mg/l.  Over 300 mg/l, we can start having troubles in extraction. Calcium: the ideal parameter for coffee is between 10 and 120 mg/l. Over 120 mg/l, we can start having an incidence in extraction.   Some advices The numbers concerning Bordeaux tap water are indicatives, and only for Bordeaux region, but these numbers can deeply change according to the city, the region or the country you live in. Certainly, the easiest would be to buy the brand of water that suits you best… but would be also the most expensive! So, what can we do? Some people might say “you should boil your water before using it”… above all, you should not do that! Because by boiling water, you would even concentrate more the components presents in water! In the long term, the best you could do is equipping yourself with filters (professional or non-professional filters), knowing what they provide you (or take from your water!). In the market you currently have a wide range of filters which can decrease the composition of calcium (hardness), chlorides or even some metals which can be founded on water installations, such as lead. As the Beatles said, concerning water, you should never stop wondering “where it goes”, and try to “fix” it, before it reaches your coffee 😉

PS. Don’t forget, temperature is as important as your water!

If water is too hot or too cold, you won’t have a good extraction of your coffee. A too cold water (<90°C) would make “under extraction”, making your coffee low in acidity and flavors, and developing “green” notes in your cup above all. A too hot water (>96°C) would burn coffee and all of its flavors, giving bitter notes as well as an astringency!