I haven't seen the term "solar salt" in Ontario. Isn't this the same salt that water softeners use? If so, any hardware store, CTC or big grocery store should have it.

This is listed on the Canadian Tire at $6 for 20 kilos (44 pounds).

Sifto Crystal Water Softener Salt
  • Improved resin clean formula
  • Inhibits rust build-up and stains
  • Pure 99.8% evaporated salt
  • High purity brine reduces maintenance
The purity looks right but I wonder abouth the "resin clean" formula? Do the chemical savvy here have any ideas if that is a no-no additive or just marketing hype?