GMSgrowsanswered grow question 4 years ago If you have an ec tester check your runoff and see how high your nutes are coming out but if your growing in soil then flushing doesn't really make much a difference unless you had way to much nutes in there. I like to take mine when the runoff is coming out under 0.4 ec 200 ppm. My water has 100 ppm so that's 100 ppm of the nutes I added still in there. .Cheers