flushing a hydro grow

okay. i'm on my first grow and have a question (faq still down). i'm a little over 4 weeks into flowering and planning ahead. how should i flush my hydro system before harvest? i've been told to go to just straight r/o water about 1.5 to 2 weeks before harvest. should i slowly change over to water when refilling system or should i just drain all of the nutes at once and go straight to pure r/o (pH balanced of course)? i've been using gh flora nova nutes the entire time. any advise would be greatly appreciated!

if your flusing with water do a whole wk before harvest, yes clear out all nutrient water then give them fresh water keep doing it till the ppm stop rising.

If your using a flushing agent like clearex you can do it 3 day before harvest.

I'm gonna use Clearex, I use the whole Botnicare line.

thanks! you guys are awesome!