I am on city well water, which is the Milford Village water system, drawn from 2 wells about 110 ft. deep. The water has gone through the local gravel and ground up limestone that the glaciers left here. The Na and CL might be there due to road salt, but I don't really know. The Village removes the iron, but that is it.
Boiling was my procedure before, and it would drop out some of the carbonate, so that the kettle had "fur" the next morning. Boiling was time and energy intensive. I also didn't know the repeatability, or the mineral content after boiling.
The RO water I get is from a store in Wixom, which is on the "City" water system, originating in Lake Huron. Good water to start with, and the RO gets it to <1 ppm for all the minerals tested by Ward Labs.