I put the filter cartridge into a Melitta fully automatic. I have tested the total hardness before and after the filter. Before the filters are at 19 dH and after that only 5 dH. Thus, the filter has a measurable impact. For any modern coffee machines, soft water is better because the lines or heaters may calcify inside the device relatively quickly. In addition, you have no longer so often descale, thereby saving money. In addition, the machine lasts longer, which puts the relatively high price again.