Corner Overflow Question

[aby]

Why does most aquariums use a corner overflow like below image?

If I am not wrong, this kind of corner overflow allow water flowing only on the surface.

Why does a corner overflow not designed like below image?

The second pic shows a corner overflow with hole at the bottom.

In my opinion, it allow water flow to the sump and circulate the entire water of the main tank, not just on the surface like the first pic.

Please tell me the reason.

 

[fijisrfr]

To keep the surface clear of Schmutz.


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[rfgonzo]

skim the surface and gas exchange

 

[SereneAquatic]

... Other than the fact that you would need a monster of a pump to keep more than an inch of water in the tank??

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[SereneAquatic]

... Other than the fact that you would need a monster of a pump to keep more than an inch of water in the tank??

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Edit... I guess the pipes height would matter. .. But still would be lower level in the tank. The water level would never rise above the pipe.

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[rjpotts]

Some overflow designs have a weir at the top (first pic) and slots at the bottom also. There is a baffle that makes the lower intake flow up and over the top so as not to drain the entire tank on the floor of you lose power. I have a 54g corner tank like that.

 

[homer1475]

Same reason its called an OVERflow and not an undeflow? Water flows OVER the wier. :lolspin::bounce2:

My center overflow has both, water flows over the wier, and at slits in the bottom

 

[hkgar]

My overflows (1 each corner) has two walls. The ouside wall has holes at the bottom middle and the slots at the top. The inside wall only the slots at the top. That system draws water from all levels.

 

[aby]

To keep the surface clear of Schmutz.


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What's a "schmutz"?

 

[Rover88]

My corner overflow is a hybrid!

There are 'slots' in the bottom, but they enter an inner chamber that goes up to the top just below where the slots on top are. This draws water from the bottom up and over, but if the flow gets too high it flows over the unrestricted 'weir' at the top.

The reason I think its done this way is that if my piping starts to leak or something happens in the overflow box, I'm only going to lose the 5-6 gallons of water in the box. Once the level in the tank is below the top of the overflow, I stop losing water.

If it drew in from the bottom, I'd lose the whole 75 gallons, or close to it.

 

[sde1500]

Why does most aquariums use a corner overflow like below image?

If I am not wrong, this kind of corner overflow allow water flowing only on the surface.

Main point of an overflow is to skim the surface of the water, remove any protein buildups on top. Why not from the bottom too? The below would be why:

if my piping starts to leak or something happens in the overflow box, I'm only going to lose the 5-6 gallons of water in the box. Once the level in the tank is below the top of the overflow, I stop losing water.

If it drew in from the bottom, I'd lose the whole 75 gallons, or close to it.

If your overflow box allowed water in from all of the water column, as I have seen some do, then if a bulk head leaked, it could drain your entire tank.

 

[Rover88]

If your overflow box allowed water in from all of the water column, as I have seen some do, then if a bulk head leaked, it could drain your entire tank.

Yeah, exactly. Mine only allows water in from the top 1-2 inches. There is an 'inflow' at the bottom of the overflow, but it goes up an internal channel and comes out at the top, just under the water line. So with my particular corner overflow (Aqueon, I think) it can't. But the OP asked why some don't have bottom holes. Some do, but they STILL feed from the top, to prevent total tank siphon is my guess.

 

[on the spot]

What's a "schmutz"?

euphemism for the stuff that accumulates @ the surface.

Left alone the surface water will become a collection of oil like slick with dust and other contaminates. Ideally the weir would only draw the surface water off. So I don't care for teeth cut into the weir.

 

[JohnnyHildo]

good points so far.
i can't remember if it was brs that mentioned it but having a "waterfall" effect is also one of the biggest contributors to gas exchange and the overall oxygenation of your system.