There are many salt-free devices for sale, using various approaches like magnetism, radio frequency, ultrasonics, pressure modulation, heat modulation, organic acids, mono/bi/trimetallic reactions, phosphate compounds, chelating agents, and various iterations of media-assisted crystallization. Some do not work at all, but I have seen salt-free scale control options in the marketplace that actually work well under certain chemical and operational conditions in reducing and even preventing hard water scale accumulation. My frustration with most salt-free vendors is the lack of consistent, repeatable, verifiable data on where, when and why these technologies will perform or not perform.
