Raindance Water Systems offers a no salt hard water conditioner. The company, which also sells conventional salt-based water softeners, explicitly states that this system is not a water softener due to the fact that it does not remove hard water minerals. Instead, it filters water through media that transforms calcium ions into calcium crystals, which do not attach to pipes.
The system is designed for up to 25 grains of hardness per gallon. Raindance recommends replacing the filters every 6-12 months, and the anti-scaling media every 3-5 years.
You can purchase the Raindance no salt water conditioner directly through the company’s website.