# Overflow question



## jmhart (Nov 13, 2007)

So, sump/overflow noob here:

Is this correct: No way no how can overflows be used as part of a closed loop system. I understand the question may follow: "Why would you want to?" but I'm just trying to understand the physics here.


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## geeks_15 (Dec 9, 2006)

Not sure what you mean. Define closed loop system.

I have an overflow/sump on my 75 gallon (journal linked below). So I know a little about them.


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## Zapins (Jul 28, 2004)

A closed loop overflow is a siphon, it will not function as an overflow if there is no bend in the pipe and an air hole.

See my diagram for how an overflow should look


















From:http://www.aquaticplantcentral.com/...automatic-water-change-system-design-diy.html


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## ghengis (Jun 11, 2008)

Yes and no...a closed loop essentially draws water from the mid section or bottom of your tank, runs it thru a pump and straight back into the tank. At no point should the water be exposed to the air, hence why it is "closed".

However, you could possibly still incorporate an overflow as part of a closed loop system. But not the type as illustrated by Zapins. If you can construct a Bean Animal type o'flow...










...whereby the uptake tubes remain submerged beneath the waterline, you should be able to end up with a closed loop, provided the water is pumped directly back into the tank, and not via a sump or trickle system or the like...


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## jmhart (Nov 13, 2007)

Thank you all for the explanation. It makes sense now. Ghengis kind of touched on the "Why would you want to?" question since the idea of CL is to not expose the water to the air, and by using an overflow, you do that anyway. 


Well, I've decided it's a moo point (you know, it's like a cow's opinion, it doesn't matter....it's moo). 

My original plan, which is my plan again, is to cut out the overflow and use one of the already drilled holes as the intake for my CL filtration, and use the other hole as the return running to a substrate level spray bar similar to what Bryce has in his 180g.


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## ghengis (Jun 11, 2008)

...ummm, just define "CL filtration" for us?? Unless by that you mean a canister filter (which is essentially a CL), and not a sump/trickle/wet-dry, then it won't be a CL...


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## jmhart (Nov 13, 2007)

Well, it'll be a closed system like a cannister. I will most likely be using some Eheim 2128s as filtration, with inline probes, co2 injection, UV and a Danner 7 for additional flow, but I may change that up.


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## ghengis (Jun 11, 2008)

Gotcha. Don't forget to post pics!!


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