Water filter in the test - superfluous to harmful

They promise soft water, less limescale, more tea enjoyment. But water filters only manage this for a few litres. One model even carried mould into the water. Does a water filter make sense? Suppliers give the impression that it is not possible without a water filter. In the test laboratory, this proved to be quite exaggerated. Filtering is usually superfluous anyway; almost everywhere in Germany, perfect drinking water flows from the tap.