Overflow Box - how to initiate the syphon

My tank does not have a hole drilled, so up to date, we have been using a power pump to pump the water to the sump. (with a glass corner, that works similiar to the overflow box)
But after much delibiration and discussions on MASA i've decided it's less risky to rather go with an overflow box, and remove the pump. (I don't want to run the risk of drilling a hole now)

I bought the reeftek overflow box, but we can't get the syphon to work. My husband tried to prime it, to initiate the syphon but it's not working.

Does anyone have some advice please, as the instructions is an A4, pictures of the contents of the box, and nothing else

 

there should be a pipe at the top of the pipe bent in an upside down U shape. You got to open that pipe and suck till you get the water moving through that U pipe.

I dont have mine anymore - and i never used mine, so that all i can think of doing.

 

on you tube there is an instruction video. cant recall what the title was

 

thanks, will try the pipe tomorrow,and try and locate the video now

 

YouTube - CS Overflow - Overview and Installation