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  1. #1
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    Internal overflow placement

    Having got one of the non-RR 75G from Big Als, I'm looking to get it drilled and an internal overflow installed. I'm talking with Harley about making the overflow but am having second thoughts about where to put it on the back wall.

    Most off-the-shelf RR tanks have the overflow in a corner but I have also seen a number of tanks where it has been placed in the middle. That has some advantages (e.g. less obtrusive) but I worry that the centre brace could make access to the overflow hard for maintenance.

    Looking for comments and experience.
    Nick

  2. #2
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    Are you drilling it on the bottom or the back of the tank? I personally would drill the back and have a shallow overflow box that extends all along the back wall (i.e shelf overflow).

  3. #3
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    The bottom glass on these tanks is tempered so, back wall it is :-)

    Hadn't thought of a shelf. Would you cut 'teeth' over the whole length of the wall?
    Nick

  4. #4
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    Cool

    put the box on the outside!! drill 2 holes and silicone the box on the outside. only way to fly.

  5. #5
    liv
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    Former Moderator liv's Avatar
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    usually the larger the box the better it is at grabing the top layer of water.
    you will get the same amout of flow through your drain hole, but it will grab more from the surface.

    moving.. so temporarily out of SW :b8:
    planning next tank, possibly 60x30x20 on 2x plasma.
    updated: 2011/05/30

  6. #6
    Senior Member CanadianGuy's Avatar
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    I'd put it on the inside if it was me. Too much of a chance for leaks and other problems on the outside. Plus liv had an excellent point!!

    I'd also go for one of the back corners...that way you can have the return on the opposite side of the tank and be sure that you're getting proper flow from the entire tank.
    James...

    "Knowing is half the battle!" ~ G.I. JOE

  7. #7
    Senior Member reefmania's Avatar
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    I drilled my 90g and centered the overflow. I built it myself and based the size on the linear overflow calculater at RC. There are two drains behind the box that lead to the sump. My return runs through a SCWD that discharges at each end of the tank. Here is a picture of the tank. The tank is 6 weeks old, and I am in the middle of the algae bloom. However, Toro, the lawnmower blennie is helping to control it.

  8. #8
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    reefmania, looking nice. Two questions:

    1) Do you have a central brace? Does it interfere with access to the overflow?

    2) What dimensions did you use for the overflow? What flow does it handle?

    Allright, I guess that is four questions :-)
    Nick

  9. #9
    Senior Member reefmania's Avatar
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    Nick,

    There is a central brace. It does interfere with access to the overflow. In hindsite, I would have made the overflow a little wider from front to back. The inside dimension from front to back is 2.5". On the next one I will build it 3" out from the back. I can still get my hand into it, but I cannot access the length inside. I have to go to the other side of the brace.

    I used 45 degree sides, rather than square 90. The dimensions are front 9" sides 3.25". This gives me 15" of overflow. I determined the minimum linear length required using 600 gph. I use a mag 9.5, rated at 950 and allowed for head loss from elbows, vertical etc. The calculator said around 9 or 10" if I remember correctly. I then upsized to what I felt would look good (proportional within tank) and would provide room for error.

    I use two return lines within the overflow. Here I compromised and can only hope it does not cost me down the road. The calculator called for 1" return. The bulkheads that I got were 3/4". So I used these bulkheads and unioned them to a 1" return off each. I am hoping that nothing more than 3/4 diamter" wants to go for a ride down either slide.
    180g with 2 x 54g corner bowfront bookends. 220 FOWLR in the works, 75g sump, 75g fuge, 75g QT.
    Solaris I4 72", 2 x 150 HQI Outer Orbit Pendants, Reeflo Orca 250, Profilux controller, Tunze 6101's and 6055's, Deltec CA Rx, PM Kalk Mixer, PM SR45 reactors.

  10. #10
    Senior Member reefmania's Avatar
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    Here is a picture of the top of overflow with brace

    Ward

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