the expaination of softners was not quite accurate but close. the minerals in your water are exchanged for sodium so in a properly working softner you don't get much salt but you will get sodium, about the same amount of sodium as the minerals it removed. It is usually not a problem for septic systems unless the water is extremely hard you can dispose of the flush water to a dry well to keep it out of the septic if you want. potassium chloride is and alternative to sodium chloride pellets, which would be better for plants and people. hard water normaly has lots of calcium and is quite healthy to drink in a lot of cases. A seperate line is a good idea. Soft water is sometimes only used for hot water but is best used for both it will reduce buildup in plumbing fixtures and reduce soap needed for washing cloths dishes and showering. The safest option would probably be to drink and cook with distilled water and take mineral pills. RO is hyped a lot but not near as good as distilled since it must have filter changes and will deliver dirtier and dirtier water the distiller will just not work if not serviced as needed but has less ability to deliver unpure water.