Overflow Question

Does an overflow have to have some type of "vent" to drain properly? Or is this only to reduce noise?
If a tank was simply drilled a few inches below the water level with a hose or pipe running down to the sump would it operate correctly? On my tank now I have a tee coming off the bulkhead, one running straight down to the fuge/sump where the water drains, the other end extended straight up. My LFS told me this is how it had to be. Like how a durso has a hole in the top of it.
Yesterday I covered the "vent" on the overflow of the tank I'm running now with the palm of my hand for a couple of minutes and the flow did not change what-so-ever. There was no additional noise created either.
I'm trying to figure out how to get my 75 to drain into my sump/fuge and I want something very simple. I was thinking about having the back two upper corners drilled with a strainer of some sort over the bulkheads. Or I could make some kind of small internal overflow box just to cover the bulkheads. Why would or wouldn't this work?

 

Do you have a picture of what your trying to describe? An overflow shouldn't have a "vent" or it will break the siphon. I guess if it is drilled it won't matter, I don't see why you would need a vent, it may help prevent a gurggling noise. I think what you want to do would work, but you may have some noise problems.

 

It will work fine. Drill the hole so that the center of it is about where you want the water level. I have been running my overflow through a hole in the side of my tank for awhile now with no problems. If you do it in your DT where snails can get to it make sure the strainer is large enough that your biggest snails can't block it or slow flow too much.

 

GuitarMan, no picture, sorry I'm at work. I should've more clearly explained what I was asking. I meant if it was drilled, not hob overflow. I figured it's only purpose was to reduce noise, just wanted to make sure.

 

Mike, would it matter if the holes are a little lower than I want the water level? I would like to keep the water level at about the same hight as the plastic frame. So I'm thinking the hole would be a couple inches under the water level. But I can make an overflow with teeth that would keep the water level where I want it, and have the water fall over into the drain holes. If that makes any sense?

 

this is the way mine works the tank is drilled on the bottom 1in bulkhead to hook the pipe the sump. The water flows over the box straight down to the drain hole it makes no noise as the pump is a little faster than the drain so there is always couple inches of water in the bottom makes no noise that is gurgling or any thing like that hope that helped ya some.

 

The bottom of the tank is tempered so I can only drill the sides. Which sucks, otherwise I would have the bottom drilled and went with something like what you have.

 

when you say vents, do you mean this? overflow "teeth"?

 

Maybe "vent" isn't the proper word to use, but in this picture I would be referring to the hole at the top of the durso pipe, not the teeth. It has been explained to me that this hole needs to be there for the water to drain properly. Without the hole or "vent" the water would kind of gurgle it's way down the drain instead of flowing down smoothly.