The general consensus is that filtered tap water is the best for coffee making. There are several types of water filtrations systems that you can use, your choice will obviously be dependent on cost. Generally, it’s good practice to use a carbon filter system which retains minerals but removes impurities. Work-top filter jugs use a small replaceable cartridge as a filter. They are quite inexpensive, and remove contaminants from your water, with the advantage of preventing quite so much build-up of scale on your brewing equipment. A more expensive 6-stage carbon/membrane/sediment filter will prove to be a longer term investment for filtered water production.