# what is an overflow box???



## padlock 08 (Jul 31, 2008)

so, what is an overflow box and how do they work?? i have no certain intentions of putting a sump on any of my systems but may do it on one of the 2 displays in my fish room. it's just that i keep hearing about them and don't fully understand them... yet

-Paul


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## imusuallyuseless (Dec 28, 2005)

http://www.monsterfishkeepers.com/forums/showthread.php?t=219465


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## Mcdaphnia (Dec 16, 2003)

That URL was an overflow that works on the same principle as an overflow box but is made of pipes. The advantage of the oveflow box is that it's less prone to be clogged on the intake because it has a "comb" of slots that draw from the surface. It can also be less noisy, although that's subjective. It may be that the box sounds less like a constantly flushing toilet than the pipes do rather than truly being quietier. Boxes have a space for a prefilter that quiets everything, but you have to trade it out at least daily with a clean one.

The alternative to either is a bulkhead fitting.


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## padlock 08 (Jul 31, 2008)

ok. i think i got the pipe idea now , thanks guys, one question though, why couldn't you just have one pipe filled with waterflowing down to the sump from the aquariums side? is it so if the power cuts the system starts again that it has all the bends?? and i don't know at all about the box, that post doesn't explain too well


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## imusuallyuseless (Dec 28, 2005)

The box uses pretty much the same concept as the pipes. There are two boxes. One inside the tank and one outside the tank. The water enters through the slots on the inside box, then proceed through the U-tubes into the outer box. There is a standpipe in the outer box that sends the water down to the sump.


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## Mcdaphnia (Dec 16, 2003)

padlock 08 said:


> ok. i think i got the pipe idea now , thanks guys, one question though, why couldn't you just have one pipe filled with waterflowing down to the sump from the aquariums side? is it so if the power cuts the system starts again that it has all the bends?? and i don't know at all about the box, that post doesn't explain too well


You have it right. The bends protect the siphon from breaking by blocking air from entering the sipon part of the pipe or U-tube. The boxes do the same thing as the bends, blocking air from breaking the siphon.

If you drill a hole through the tank and attach a bulkhead fitting in it for the pipe, you can have just one pipe. In the pet shop you can see new aquariums that are "predrilled" for this method. Usually there is some kind of wall blocking it off from the rest of the tank, and keeping fish from being sucked in or debris from blocking the hole.

You can't safely have a pipe siphoning over the top. It may siphon faster than the pump can keep up. If the power stops, the siphon will keep going and overflow the sump. Then when the power comes back on, the sump will empty into the tank, no water will come back, and the tank will overflow, the sump drain empty, and possibly damage the pump. The bends (or boxes) will slow the siphon until it matches the pump rate. Correctly leveled it will prevent the sump from overflowing even if power goes out. and you already understand that it will preserve the siphon so that the tank doesn't overflow.

Imusuallyuseless' post has a good explanation of the box system.


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## padlock 08 (Jul 31, 2008)

thanks guys, i think i understand them now, last question (i promise :lol: ) in the box inside then tank, will the pipe drawing the water from the box not run dry and lose it siphon after the power stops and the water level drops below the slots?

-Paul


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## imusuallyuseless (Dec 28, 2005)

In a properly designed overflow there are only slots near the upper portion of the box inside the tank. This allows water to stay in the bottom of the box. So even when the pump is not running there should always be enough water in the bottom of both boxes to maintain the siphon of the U-tubes.


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## padlock 08 (Jul 31, 2008)

but will the siphon not drain the box and keep doing that until the water supply stops, i.e when the water level drops below the slots, the will the box just not get drained??


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## imusuallyuseless (Dec 28, 2005)

The height of the standpipe on the outside box keeps the water from draining completely.


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## padlock 08 (Jul 31, 2008)

ahhhhh, thanks for that, i completly understand it now    thanks for the help guys :thumb:


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