Types of Overflows, an Illustrated Guide

Neil H

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This thread is specifically designed for people just entering the marine hobby, In most (if not ALL) circumstances a sump is required to have a successful marine tank.

Trying to balance a pump from the display tank with a pump from the sump (a two pump system) regardless of safety valves, cut off switches etc is inviting disaster :nono:

Either the Sump must be fed by gravity (when the sump is located below the DT) or the DT must be fed by gravity (when the Sump is above the DT) ...

Now depending on your specific design criteria and space available there are a number of possibilities when designing an overflow (whether this is a DIY project or a a custom build by a LFS)

The list below is not an exhaustive list by any means and I encourage other members to add as they see fit...... but please add images as well as descriptions

There are two basic categories, a drilled tank and a non drilled tank. A drilled tank is infinately more superior to a non drilled tank, a non drilled tank relies on a syphon system.

Option 1 - Non Drilled Tank, Overflow Box

9114c92af5e8b29e.jpg




There are a variety of commercial units available and several DIY versions in the MASA DIY forum. I do not like these and would not generally recommend them, although some people have been running these systems for a long time with little hassle.

Option 2 - Drilled Tanks

Here follows a series of images which show different overflows for drilled tanks, be the hole in the base or the side panel. Note that these images are schematic only and that they show the concept not specific measurements. I would strongly recommend re-enforcing every hole drilled with a 6mm glass patch with the same diameter hole drilled in it, this may be viewed as overkill but rather safe than sorry ....



Corner overflow V1
9114c92a9a23bb59.jpg

This overflow takes up little space (reef real estate), is an easy DIY project, can be covered with persbex etc to hide the inner workings, but unlike the coast to coast versions shown below, does not have a great surface skimming ability.

Corner Overflow V2
9114c92a9a42a4c5.jpg

This overflow takes up less space (reef real estate) than the square corner overflow box, is an easy DIY project, can be covered with persbex etc to hide the inner workings, but unlike the coast to coast versions shown below, does not have a great surface skimming ability. Due the the extremely small space available to work in, making any adjustments to the durso etc is difficult.

Central box overflow
9114c92a5aea3715.jpg

This overflow takes up little space (reef real estate), is an easy DIY project, can be covered with persbex etc to hide the inner workings, but unlike the coast to coast versions shown below, does not have a great surface skimming ability (it does however have a better surface skimming ability than the corner overflow options)

Skinny central overflow V1
9114c92a594200c8.jpg

This overflow takes up very little real estate in the tank and exits out the side panel with a tank connector. the skimming ability is not particularly great and one runs the risk of getting things stick in the overflow due to it being so thin.

Skinny central overflow V2
9114c92a5946b0de.jpg

Very similar to the above version, this simply exits out of the base as opposed to the side panel.

Internal overflow box
9114c92a5ae97b0c.jpg

Situated inside the tank but only in the upper portions this version of an overflow takes up little real estate, Skimming is on par with the versions above but this version MAY proove noisy as adding a durso in such confined space may be problematic

External overflow box
9114c92a59477834.jpg

From a real estate perspective this is the best overflow design as it takes up zero space, surface skimming is acceptable, however the external box attached to the tank may look unsightly

Coast to Coast V1
9114c92a99fce4eb.jpg


This offers excellent surface skimming but some feel this overflow is unsightly.

Coast to coast V2

9114c92b4fc05a1d.jpg


Again, excellent surface skimming but takes up real estate and is unsightly.

Skinny Coast to Coast
9114c92a9c0393a3.jpg

Good surface skimming, and takes up little real estate but shares the risks as outlined with the other skinny overflows. A similar version to the image above is often used where the hole is in the base, as shown in the image "skinny central overflow V2" shown above

Remember all overflows should be constructed in the same thickness of glass as the sides of the tank, not thinner

Hopefully you can now make an educated choice as to how you want your new tank to be designed and built
 
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Neil H

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This is my overflow setup located on the side of the tank .... I stand to correction but also C2C kinda overflow just not front to back flow but rather side to side .... durleo, isn't yours the same?
sidefilter2.jpg

interesting design, as you say a type of C2C, but i dont understand why you would want an under over design with rubble in the under-over .... would this not trap detritus before it hits the skimmer ?
 
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Tank was bought in 1986 ..... this original design was meant for trickle filtering .... believe or not, the first compartment house a wooden airstone skimmer and it only 10cm's and then the next had like bioballs and wool then this overflowed to a "dry filter" just with bioballs in and lastly to the sump .... but now have nothing in the compartmets but I'm sure with all these new things like bio pellets and things I'll find something to go in there .....
 
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awsome
 

RiaanP

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Internal overflow box
9114c92a5ae97b0c.jpg



Skinny Coast to Coast
9114c92a9c0393a3.jpg

Neil, I got a combo of these two types.
Skinny coast to coast, and only at the top.

10944b4611ca98546.jpg

Note, tank is lying on the back pane in this pic. The double glass part on the left is the euro bracing.
And I have two outlets. Only one shown.See the T-piece behind the glass. On the top, I placed an endcap with airvalve. That creates an external Durso.
 
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dallasg

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nice one!
 
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Nice thread, Neil, thanks for your efforts in putting this summary together.
For the record, here is my system, the external overflow box.
With it being enclosed in a cupboard, I overcome the unsightly look of it.
Wide surface skimming makes it very effective, easy to control and work on.

0381440c.jpg
 

Neil H

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thanks for the additions and comments,

Durleo, a centre overflow is one that i have ommitted ..... hopefully Lanzo will post otherwise I can whip up a design tomorrow
 

neo

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May I correct ? It's Dewalds tank, not Lanzo.:)
It uses a c2c channel which channels the water to the corners with the water then running down to the base and out.
They then use the opposite 2 corners in reverse configuration as return points - nice surface skimming.
 
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Skinny central overflow V2

Hey everyone

I have Skinny central overflow V2 and still havign a few issues making it completely silent

I have reduced the overflow as much as I can will a ball valve but it is still noisy......any ideas?
 
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