We had planned it that way too, but so far I haven't needed to install the tap for "normal" tap water. I also like the demineralized water. It tastes different but also good. Honestly, though, I've never really liked "Berliner Rohrperle" very much. It was better elsewhere.
We have very hard tap water in our residential area. The lime in the water is not detrimental to health, rather the opposite. That’s why we don’t buy bottled water but drink only tap water. The coffee machine is descaled once every 4 weeks, dishwasher too, and the washing machine has been running for 10 years without descaler. And that is really no work.
This discussion is completely pointless if we don't know the hardness level of your water.Same here! We are really quite at the upper end regarding H2O hardness. Coffee actually tastes better with soft water - but the separate filter in the fully automatic machine takes care of that. Otherwise, provided proper care, we have not lost either the dishwasher or the washing machine over all these years. Of course, it is annoying when the sink edge and kettle have to be cleaned regularly. Even more annoying, but especially more costly, would be a descaling system.