So the hole needs to go in the Utube, but only if the tube is fully submerged while the tank/sump/overflow are working normally... if the tube is out of whe water at all when its working then no hole is needed. right? thats what i took out of it...
well i thought that the only way water gets from the DT to the sump is throught the overflow... and my thought process was that even if the power goes out, the water level in the tank will drop untill its level with the overflow, and then the siphon would break anyway because there wouldnt be any more water in the overflow to drain into the sump...
also, a picture would still clarify things much more... a picture is worth 1000 words to me