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Overflow Diagrams


Tigahboy

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Just finished the 3 I'm most familiar w/ (i.e. have made/used for my own tanks).

 

hope it helps...

 

stockman.jpg

 

extdurso.jpg

 

durso.jpg

 

I'll try to do a breakdown of pros and cons of each overflow type as well. After I rest a lil tho. -_-

 

EDIT - I am adding a diagram for the Herbie overflow since wombat was so kind enough to contribute them to this thread.

 

Herbie Overflow

Diagrams courtesy of Matt Wandell (wombat)

 

Herbie1.jpg

 

Herbie1.jpg

 

You may add either a strainer at the top of the standpipes or an elbow. I've seen both. Some even add a durso for the higher (secondary) standpipe. But the main elements of a Herbie include a lower, primary standpipe with a gate valve to control the water level in the overflow box and a higher, secondary standpipe.

 

There are discussions about the Herbie throughout this thread, please do a search for them within this thread for more information.

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*bookmarked* :ninja:

 

Thanks Tigah for the very useful information. Great diagrams.

no problemo. just doin my "job." =) haha.

 

will post more info about each sometime next week.

 

and if y'all have any questions or diagrams need clarification, lmk.

Edited by Tigahboy
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Which one would you suggest, the durso, or the stockman, for an internal overflow?

 

Thanks for taking time to put the diagrams together.

Stockman. I'll elaborate more when I do the pros and cons chart for each.

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thanks for this, Tigah. I have a question:

 

I recently bought a used Oceanic 40g from an LFS that was going out of business. It came pre-drilled with a 1" bulkhead w/strainer near the top right and a 1/2" return near the top left. Do you think

 

1) I should use the "external durso overflow" setup? Will this provide higher gph than just a regular drain (i.e. no durso)?

 

2) Will one 1/2" return provide enough flow for softies & LPS? I have no interest in keeping SPS. I think I may put a "Y" on the return with some locline attached.

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gawd. the return will generate a lot of pressure. what kind of flow do you want in the tank. for a target of 15-20x turnover, i would want at least 3/4. lots of pumps have 3/4 outs and easier to reduce the pressure.

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3/4 will give you more pump options to get that kind of turnover. a stand pipe won't increase your flow. flow capacity is limited by the size and the depth of the hole(s) of the standpipe to the water level.

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thanks for this, Tigah. I have a question:

 

I recently bought a used Oceanic 40g from an LFS that was going out of business. It came pre-drilled with a 1" bulkhead w/strainer near the top right and a 1/2" return near the top left. Do you think

 

1) I should use the "external durso overflow" setup? Will this provide higher gph than just a regular drain (i.e. no durso)?

 

2) Will one 1/2" return provide enough flow for softies & LPS? I have no interest in keeping SPS. I think I may put a "Y" on the return with some locline attached.

 

External durso will not give you higher flow thru. But just a simple bulkhead at the back will be very noisy and the flow thru won't be constant (i.e. siphoning faster and slower).

 

two 1/2" returns would be more ideal.

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External durso will not give you higher flow thru. But just a simple bulkhead at the back will be very noisy and the flow thru won't be constant (i.e. siphoning faster and slower).

 

two 1/2" returns would be more ideal.

 

There's a post written by wetworx about flow rates depending not just the size, but the position in the back wall of the tank. Briefly, it says that the closer the hole to the top of the tank, the slower the flow rate will be. So yeah, it wont be as fast, but that doesn't mean that'll be turtle-speed flow rate. A part of the wetworx post as follows

 

Yep. The calculations I did come up with that figure, now keep in mind that my calculations are based on a vertical hole which technically wont drain as much as a horizontally mounted hole (simple example: a 1" hole at 1/2" depth mounted verticaly would only be half underwater yet a 1" horizontal/flat hole under even 1/4" water would be completely covered). So if you were to put a hole on the bottom side of a tank, as long as it is vertical, it will have slightly less pressure on it than a bulkhead mounted on the bottom glass because of it's height. So a bottom hole will have a slight flow gain on a side hole, but I am not going to redo my calculations because were talking a minimal gain here, considering we would be at 12" or more of depth the flow on a horizontal bulkhead is already in the hundreds. More flow can be lost with screens over the bulkheads and accumulation of crud on a bulkhead's intake, easily over 20%. That's why I would never go with a bulkhead less than 1" unless we are using it for less than 100gph, or you are sure to prefilter the water enough to prevent clogging (D, I think you will be fine as long as you put a sponge or screen in your overflow above the bulkhead to keep any chunks away).

Just short of graphing the chart with line curves I have for flow by cross referencing hole diameter with hole depth, I can post the following:

1"bulkhead @ 1" depth=338.6gph

1"bulkhead @ 1.5" depth= 414.8gph

1"bulkhead@ 2" depth=478gph

1"bulkhead@ 3" depth=586gph

1"bulkhead@ 4" depth=677gph

1"bulkhead@ 5" depth=757gph

...if you even need to know what the possible flow for a hole at a given depth is for more flow you dont have a nano anymore, and you are in the wrong forum.

3/4"bulkhead@ 1"depth=190.5gph

3/4"bulkhead@ 1.5"depth=233.3gph

3/4"bulkhead@ 2"depth=269gph

3/4"bulkhead@3"depth=329gph

3/4"bulkhead@4"depth=381gph

...you can draw the rest of the curve from there.

1.5"bulkhead, I dont think anyone needs these on a nano because 1" is enough for most tanks up to 40 gallons, and remember...a 1.5" bulkhead has more than double the intake area of a 1"...so were @ 933gph at just 1.5"deep.

 

Cheers :P

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How do you plan where to drill the holes for an external Durso setup? I've seen you do that in rbaby's tank and your 15s and was planning on emulating when my 33 arrives.

 

Chris

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neanderthalman

If you use a strainer basket, like in the drawing, it will skim the surface. With the external durso, you don't have an internal overflow box to do that skimming, so you compromise.

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If your skimming then air is coming in and the hole in the top making the overflow a durso overflow doesnt do much does it. The hole keeps a full siphon from ever forming but that hapens when skimming too doesnt it.

Edited by Opcn
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neanderthalman

My understanding is that the hole isn't a siphon break, it's purpose is to disrupt the vortices that form around oveflows. It's a shut the hell up hole, 'cause without it, the overflow will be very noisy.

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