Toms Aquatic Overflow

[KyleWhitaker89]

I currently have a toms aquatic over flow and like it for the most part, only problem im having is when the return pump is turned off it tends to flood the sump before the siphon is broken. I have read on many other threads about drilling a small hole in the return right below he water line but don't think that will work for this set up...any ideas?

 

[Reefing Madness]

Why wouldn't drilling holes in the lines work? Works for all the other overflow boxes with lines.