My spinbrush 50 worked fine for about 5 minutes out of the box. After the first dirty water dump it stopped sucking because the yellow float “ball” would immediately go up and stop the flow. I found that the sleeve filter over the yellow float was indeed the culprit (as stated in a previous post). It restricted the airflow just enough to cause the problem. I tried rinsing the filter really well but even a little bit of air constriction was too much. I took it off completely and that did the trick. I don’t know what long term effect this might have on the machine, but it’s a good short term fix. Btw, if you have a lot of foam in the dirty water it will cause the same problem - the yellow float will stay in the up position and stop the suction. In this case dumping the dirty tank and rinsing out the foam will fix the problem.