After you take a leak or a crap in your toilet, there's that little metal handle thingy on the side of the tank. You push it down and it all goes down the hole. Hope this answered your question. All kidding aside, flushing is what some ppl like to do to their plants before they harvest in order to purge the nutes out of the plant. I, along with several extremely knowledgable long time growers on this site don't flush before harvesting. I did it one time and the plant seemed to suffer more than anything. I think that the last week of flowering is when the plant needs food the most to finish up it's work. It has been MY experience, and in MY opinion, flushing is NOT necessary. If you harvest when the plant is ready, then dry it and CURE it properly, you'll have some great smoke. Like I said, I flushed before and didn't see any difference in the finished product. Good luck.