I too had the same problem, I am using a Boyu Sump pump with 1100 liter/hour capacity. The Weipro box says to use 1600 liter/hour capacity. When I leave the water level at the mark indicated on the cylinder, the foam is just not high enough to reach the collection cup. So I raised it to the neck level at the bottom of the collection cup, by turning the valve at the output very slowly, and now the foam is rising to the top of the rising curved tube. This is the best adjustment I think. I will know in a day or so if the collection is happening or not. Will keep you all posted.

By the way, this is my first 2 minutes after registering at this site. I found this by doing google search on weipro 2012. Amazing to know that internet can bring us all with same problem together. This is my first marine tank and I will need a lot of help. Just added 2 clowns and carpet anemone, 2 tube worms and a live coral 2 days ago. Have my fingers crossed !!!