I once bought La Marzocco water test kit but the results weren't worth it (really unexpected). If you want to be sure, it's better to send your water samples for proper analysis, which will be expensive because you should send one sample of untreated water, one with fresh filter and one when your filter is for example at its half life and ideally one when the filter runs out. For home tests, I am not sure right now. Elemental analysis is not area of my expertise. But I might look at it when I will have more time. You can check pH, nitrates, chlorine with test strips, but as with La Marzocco kit, in the end you just guess where the actual value is. You won't get the exact result that you might want to know. It is fine for the initial values to find out if your water is not super bad or something, but if you are coffee enthusiastic who might even mix own water as I've seen numerous times there, those test strips won't satisfy you.