There isnt one!!! I NEVER flushed, EVER! Leeching is meant to use up any unused nutes stored in the soil/substrate/plant so the bud tastes nicer. I ran experiments, doing blind taste tests and no one could tell which had been leeched and which hadnt. IMO, depriving your plants of food in the final 2 weeks is robbing the grower of yield. Nutrient companies make the most of this by creating another product to sell that "improves flavour/taste/whatever". My challenge to EVERY grower out there is to do a half & half test to see if there really is a difference and you can tell which is which. If you can, you are overfeeding your plants, if you cant, your yields will improve as a result of you stopping leeching!!! LMAO, I wonder how many will do it???