RO would go after the sediment filter and before any water softener. Nothing will change in the storage tank. The waste water is fine for almost anything. It will have a higher mineral content but the filters actually remove quite a bit. Just test the waste water but I would not have a problem using it in the garden or lawn as rain water will easily dilute and wash it away. You just don't want to use it after a w,ater softener that adds Lotsa of sodium, it will burn up your RO filters quick and have higher sodium in your waste water
so storage tank,i have a 250 gal IBC tote down there im use for nutrients when i feed,reason im asking,got the trash can grow going,found out the well water was the issue,got ro water filled the can and every thing cool,every 2 days was refilling it,ph ppm right on cue,so im thinking the condensation water coming from the house drain line is like ro water,ph 7 and ppm 33,checked ro water ph 7 ppm30,pretty much the same right,well to save money on ro water started using the condensation water,top off 3 times over a week,well yesterday,i started getting a spike in ppm like 1400 ph 5.1,so i added just plain tap water which is 7.24 ppm 315,ok rasied the phto 5.2 but wouldnt go any higher but ppm did,so siphoned all water out today rinsed the roots,had a sad plant boy i mean sad,so filled with ro water,added all the same nutes and still had 5.2 ph ppm right at 1100,well the recipe calls for 5.8 to 6.2 ph ,i been running 6.so i added 27 grams each of magnesium sulfate and calcium nitrate,just a few points difrent,im like what is going on,so had enough room for 2 more gallons of water,u,sed the tap water because the ppm and ph so high i figured it would balance out to right at 6 and 1200 ppm,put 1 gal in did raise the ph to 5.4,added 1 more gallon and ph leveled off at 5.8 and ppm at 1200,so i left it,check in morn to see if it still there,i have no clue how to raise the ph witout rasing the ppm,can you use to much
hydroguard and maybe this is why im having issues,every other top off i use 60 ml of it