Going to install a tankless water heater (propane) and water hardness is 19-26, in NW Montana. One retired master plumber told me to install a Aqua Pure AP430 water filter for the scale. Do not really want a softener since I had bad experience with last one and all the resin beads throughout the plumbing system. Most plumbers give me a "deer in the headlights" look when I bring this up. All insist the only way to protect tankless systems is with a softener. Please help with some good advice or fact sheet on this problem. I do not want to ruin a new tankless system if I can help it. Household is three adults (70+ years) so we will not be running hot water 24/7.