Thickness of overflow slot... please help?

anaya

Shh Lets Not talk Cost!
I'm doing an external overflow on a 75gal. I'm gonna do a slot opening instead of teeth. Length wise the opening will be 12" I just do not know how tall to make it?

Can anyone point me in the right direction.....please!!

Antonio
 

nanonubey

Shogun
I use eggcrate on my overflows and i make them two squares high. The water level is always at the bottom square.
 

anaya

Shh Lets Not talk Cost!
so you do the slots at 1" and the water flows over at around .5". how much flow is that with?

Antonio
 

NanoReefWanabe

New member
the height of the weir water is not only dependent on the amount of water but the width of the weir...
typically people have the weir cut so that the water level will still be hidden by the trim and remain at a safe level that doesnt risk flooding. since your tank is trimmed i would say have the weir cut to about an 1/8" below the plastic trim...at 12" wide your weir height will likely be more then 1/8" so the water surface should always remain hidden...
 

anaya

Shh Lets Not talk Cost!
okay, so, 1/8" below the trim at 12" long and the weir will keep the water line hidden behind the trim. I apologize if I'm just not understanding. I know the length will be 12" but what should the height be? L x H = 12" x ?H? Or do I just cut a 12"L U-shape from the top of tank to 1/8" below trim? |______| or cut a rectangle in the back.

I apologize again, I would try to draw a picture but no program to do so on my computer.

Antonio
 

NanoReefWanabe

New member
if it were my tank i would try to go considerably wider then 12" (depends on the size of the tank but 12" wont provide very good surface skimming on a tank any bigger then 10-20 gallon.

you dont want the cut to be square in the corners, you want the corners to have a large radius to prevent it from cracking...
 

nanonubey

Shogun
Here's a picture of my 20l frag tanks overflow. I make them 8'' wide by 4'' deep by what ever the tanks height.

<a href="http://tinypic.com?ref=soy5pt" target="_blank"><img src="http://i55.tinypic.com/soy5pt.jpg" border="0" alt="Image and video hosting by TinyPic"></a>
 

nanonubey

Shogun
if it were my tank i would try to go considerably wider then 12" (depends on the size of the tank but 12" wont provide very good surface skimming on a tank any bigger then 10-20 gallon.

you dont want the cut to be square in the corners, you want the corners to have a large radius to prevent it from cracking...

My 8'' wide overflow works great on my 120. Factory overflows are around the same dimensions as mine. I measured a AGA 180 overflow for my diy's specs.
 

nanonubey

Shogun
Here's a picture of my diy overflow on my 120.

<a href="http://tinypic.com?ref=ot21a8" target="_blank"><img src="http://i54.tinypic.com/ot21a8.jpg" border="0" alt="Image and video hosting by TinyPic"></a>
 

NanoReefWanabe

New member
i never said it wouldnt work, just that a longer overflow will skim the surface of the water better as it wont have the weir height that a shorter overflow has, essentially skimming just the surface of the display and not the top 1/2"

BTW your tank is beautiful
 

anaya

Shh Lets Not talk Cost!
First of all; Thank you all for your help, tips and advise! Also being so patient with my persistent questioning.

ok Got it. Finally! I'm gonna do a coast to coast like the BeanAnimal, except exterior. I have access to a 7/16" glass router bit, that I will use to make 4 slot cut outs 10" long with the bottom of the slots 1/8" below the trim of tank. I will start the slots 2" in from the sides of the tank and have 3 1.5"+/- spaces between each of the 4 slots.
| ---- | <- that is as close to a drawling as I can do.

Again thank you all
Antonio
 

nanonubey

Shogun
i never said it wouldnt work, just that a longer overflow will skim the surface of the water better as it wont have the weir height that a shorter overflow has, essentially skimming just the surface of the display and not the top 1/2"

BTW your tank is beautiful

Thanks :beer: I just offered a easy way of doing it, it's definitely not the only way to do it. :D
 

das75

New member
I'd just do a single notch out the back rather than slots. For width and height here's a link to a Excel Spreadsheet (overflow capacity calculator).

It's neat to play with eg, a single opening 12" wide, if the water is 1/4" above the lip your flowing 390gph.
 

anaya

Shh Lets Not talk Cost!
das75,
I cant open the calculator for some reason?? I go to the site and when I click on the calc link it asks me to select a program to open with? I'm using a Mac and tried all I could think to try but none worked.

The reason for doing a series of slots is to hopefully retain some of the structural integrity of the back pane of glass. I guess what I am thinking is that a slot that is 40" in length will be weaker than a 40" slot that has three braces in it. Almost the same idea/reason 4'+ tanks have a center brace on the rim? If that sounds crazy please explain why.

Tank is a 75 and will have between 500 and 750gph flow through the overflow.

Antonio
 

das75

New member
calculator is a Excel spreadsheet so need to open with that. Not cut and pasting cleanly but a 16" slot, at 500gph water is a 1/4 deep.

Take a look at this excellent build thread (pg4 , post34) where the builder used a hole saw (eased corners) then connected the holes.
 
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