We have received several inquiries as to whether "distilled water (demineralized according to VDE 0510)" from the drugstore/supermarket can really be used without any concerns and what other possible alternatives are available. With this article we would like to provide some clarity for you - we hope we have succeeded ;)
Deionized or distilled water in general
In principle, a healthy person can drink distilled or deionized water without concern, even exclusively.
With a healthy and varied diet, our body absorbs enough minerals and trace elements through normal food. There are even many countries in which distilled water is industrially bottled and consumed as particularly pure drinking water.
"Distilled water (VDE 0510)" from the drugstore/supermarket
What many people don't know: The "distilled water (demineralized according to VDE 0510)" sold in Europe by DM, Klax, Kerndl and many other manufacturers is tap water that has been deionized by reverse osmosis and is therefore - contrary to some people's opinions - an excellent and safe basis for making coffee. We have tested some of these products for purity as part of our product development, with unreservedly positive results. As "Distilled water (demineralized according to VDE 0510)" is explicitly declared for use in the laboratory and for aquariums, it must be free from harmful substances/impurities - manufacturers cannot be negligent here.
The note "Not suitable as drinking water" refers to the fact that an unbalanced diet combined with the exclusive consumption of demineralized water can potentially lead to deficiency symptoms. However, this is irrelevant for our application, as the water is mineralized again by pure coffee water before use.
Alternatives and personal recommendation
Our recommendation and probably the most sustainable method of obtaining demineralized/deionized water is a reverse osmosis system - good systems are already available for less than EUR 70, which can be connected to the tap without any major installation on demand. The demineralized/deionized water obtained from this can be used directly as the basis for our product. Alternatively, a ZeroWater filter may also be worth considering.
BRITA, BWT & Co are explicitly NOT an alternative!
Tap water filtered through activated carbon (BRITA) or softeners (BWT) is not completely free from limescale/minerals and certainly not from impurities. This means that the benefits of pure coffee water in terms of taste, appliances and health cannot be guaranteed.