Burmeseanswered grow question 3 years ago Hi there, Even if it is rain water, you don't need to worry.All you have to worry about is your water pH and ppm after mixed nutes including pH down solution.Always make sure to run off some water from the bottom. keep your pH around 6.0~6.5 for both in and out.Also in soil,the less nutrient the better to prevent toxicity or lockout.Good luck and Happy Growing... ✌️