Well you can try to flush organic soil but you are pissin in the wind. In the end it all depends on what your needs are. I grow indoor, organic as possible, in soil. Yield doesn't mean anything to me, quality and taste are my main concerns. Yes I am that friend that has the smallest buds from the same genetics but some reason, mine smell stronger, taste is stronger and they are just as pretty as their hydro counterparts.
I water with RO water from beginning to end. Everything else is mixed in the soil. I may use tap water once or twice to bump cal-mag but thats about it. Now what I do is dry them out big time. Last 3 weeks of life they don't get water.