great subject...you dont want shit in the water, you add these with the soil well water has lots of lime calicum and is prone to lockup due to high ppm
so through the softner and then through the water purifier under the sink...yes this system will use salt to draw out these sediments, you will still need to invest in further filtration but softeners will improve the quality dramatically
now i know i do have a water sofiner and a undersink filter but i allway thought it would be better for the plant . but i am wrong and now i know sorrywell water is very hard and has high EC/ TDS this water is less than desireable for growing.