Overflow with mid and low slots

[slowngreen]

Ive seen a few overflows with middle or even bottom slots for water to go through, which seems great because its should keep the water cleaner since its not just draining the top, correct?

 

BUT, incase of a power outage, you would have to be there to close the valves every time or have a huge sump wouldnt you or is there options around this?

 

[Rollermonkey]

Not necessarily, depending on what kind of overflow is being used. With a stockman, the siphon would break once the level in the tank dropped below the level of the pipe.

 

But yeah, you could drain half of a tank easily with a herbie and bottom slots.

[slowngreen]

Ive been googling around, thinking maybe some kind of electric pvc valve would be a good fix, so maybe it would shut the second it lost power. No luck except for very expensive items.

[Rollermonkey]

You know what KISS stands for? Keep it super simple. (or close enough )

 

Stay away from fancy stuff like that. just when you start to trust it, it'll fail and flood your house / apartment.

 

If you want low and high slots, just use an overflow that won't permit the tank to drain that far.

[AZDesertRat]

No need for any valves. The water level will only drop to the level of the standpipe inside the overflow box. Once the standpipe opening is exposed the siphon quits and you have the best form of backflow prevention known to man, an air gap. We all know wate rcannot jump uphill so it is foolproof. Make your stanpipe the height you feel comfortable with and you have room in the sump to contain. As long as you maintain sufficient room in the sump its never a concern.

[Apexdv]

+1 for this guy ^^

[slowngreen]

I have a herbie style now which works great but Im always thinking about my future tank is all.

 

Part I was really questioning in my mind is if you have the standpipe at a good height, and you have mid or bottom slots on the overflow box, will the bottom ones actually have much water go through them? I think Im confusing myself with the idea.

 

Well I guess the water on the bottom would fill the overflow box real quick wouldnt it? Faster than top water would drain since it would be somewhat pressurized.

[AZDesertRat]

If you have good circulation in the display they really don't add much if any benefit. I prefer surface skimming myself which is what the teeth on the top of the overflow box provide and my powerheads keep things in suspension so they eventually reach the surface or settle in a quiescent area to be siphoned out.

[slowngreen]

My teeth are at the top now too but seems to take forever for any type of garbage that gets into the display to find the overflow. I have one on each side wall facing the opposite wall and my overflow is in the corner. Maybe I just need to play around with the powerheads. Would both on one wall face the opposite wall still be a productive current?

[nibor]

You should research "surface skimming".

 

The theory is that for an overflow to be most effective at getting organic material out of the display, you should take the thinnest layer possible at the waters surface. It is said that this is where the proteins and other organic material are most concentrated, attracted to the air/water interface.

 

This concept lead to the "coast to coast" overflow as proposed by Anthony Calfo, an overflow running the whole length of the tank with no teeth to take the thinnest layer of water possible.

 

Slots lower in the overflow box go against this theory and as you mention make the standpipe design critical in setting the water level. The overflow is no longer an overflow.....

 

Edit: +1 AZDesertRat except for the bit about teeth. Teeth on an overflow reduce surface skimming by reducing the length of the sheet of water and therefore making it thicker.

[nibor]

My teeth are at the top now too but seems to take forever for any type of garbage that gets into the display to find the overflow. I have one on each side wall facing the opposite wall and my overflow is in the corner. Maybe I just need to play around with the powerheads. Would both on one wall face the opposite wall still be a productive current?

Try to create a gyre, a circular current through the tank that leads to the overflow. Within this current, you want the flow to be randomn. As a starting point, try pointing two powerheads towards each other and putting your return in the opposite back corner to the overflow and facing the front glass.

 

After that, you just need to play around with things depending on your rock work, tank shape and pumps.

[AZDesertRat]

Yes and no on the teeth.

By adding the teeth you reduce the surface area of the overflow thus increasing the velocity so it tends to draw water to it better. This principle has been used in treatment plant clarifiers for centuries. With a continous overflow weir you do not achieve the same velocity, the water kind of meanders over too it unless pushed by the powerheads. I refer teeth or V notches and it is a proven technique.

 

I have my two powerheads at opposite ends of the display, both about 6-8" below the surface and pointed slightly up. One is pointed more towards front center and the other rear center so as nibor pointed out I get a circular motion so everything eventually makes its way to the overflow box.

[slowngreen]

Ok good info guys. I hadnt even seen an overflow without teeth, gives me something to go research and learn about. I have my powerheads pointing slightly down at the moment but I'll play with them now and see what I can change. Im getting my algae problems under control finally I think so getting my water perfectly clear is a new goal.

[djfrankn]

Could it be turnover ratio/hour plus flow direction in your tank your concern about skimmer performance and perhaps the algae problem that you mentioned last?

[slowngreen]

Sorry but what? Could the skimming problem be my algae cause, is that what your saying? The flow inside the tank is pretty good, doesnt seem to be any dead spots anymore after some moving stuff around, havent had any cyano on the sand bed since my last water change which is new for me lol so Im happy about that. Just seem to be any things that get blown off the rocks circulate the display water non stop.

[pazzo40]

No need for any valves. The water level will only drop to the level of the standpipe inside the overflow box. Once the standpipe opening is exposed the siphon quits and you have the best form of backflow prevention known to man, an air gap. We all know wate rcannot jump uphill so it is foolproof. Make your stanpipe the height you feel comfortable with and you have room in the sump to contain. As long as you maintain sufficient room in the sump its never a concern.

 

Can this be applied to any overflow system?