overflow box - c syphon

[whitsunday]

I put plastic airpipe up to top of syphon put u tube into overflow which had water on both sides............sucked out air.........syphon full of water..........next problem..........hooked up mag 12 to sump (full of water) and turned on system..........

water rose in tank to near overflowing so i shut down pump...........syphon does not seem to work that fast...........am I missing something?


Glenn