I got stones out almost always. A couple of times I got out very little, but that was not because there was no more to come out. I believe I had just gotten to a point that what ever section or area of the billiary tree was emptying at the time, was either near the end or there was an obstruction that limited how much got out during that flush. I am not going to quit flushing routinely (now about every two weeks) until I get nothing out for three or more consecutive flushes. Then I will go to once a month or once a quarter forever.