slim overflow design/math

Discussion in 'Pumps and Waterflow' started by samiam, 8 Mar 2012.

  1. samiam

    samiam

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    hey guys,

    I'm in the process of building my slim overflow for my 45g cube (24x24x18"). I'm going with this design:

    http://img.photobucket.com/albums/v189/slammin/fishtank/45g starfire cube/slimoverflow3.jpg

    the plan is to make it 10" wide with a 1/8" gap for the drain.

    my question is, how much flow can the 10" wide overflow with 1/8" (3mm) gap handle? I'll have a 1" bulkhead installed at the bottom.

    will it be able to take ~600gph (i believe thats the max a 1" drain can do)?


    thanks!
     
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  3. Albert Terego

    Albert Terego

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    Try this for an indication. I am assuming the return is gravity fed.

    CalcTool: Gravity-fed pipe flow calculator

    Looking at your design, I would calculate from your 1 inch overflow outlet to the end of the pipe which goes into your sump. If it is a straight drop from overflow to your sump i.e. perpindicular to the floor then your Pipe Length and Drop would be the same figures.

    You will also need to consider if a 10" by 1/8" overflow area is going to be large enough. I'd guess it would be because the area of the rectangular part of your overflow is larger than the area of the outlet (surface area of rectangular portion = 1.25 square inches, surface area of 1" outlet = 0.787 square inches)
     
  4. RiaanP

    RiaanP Moderator

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    Metric dude, metric...

    10inch is 25cm
    600gph is 2271L/h

    1 inch bulk head is too small
    And would make the overflow length longer. 30 to 40cm. Up to you to convert that to imperial...:)
     
  5. samiam

    samiam Thread Starter

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    thanks a lot guys! its good to know that the 10" overflow will handle more than the 1" pipe...

    Albert: that calculator is exactly what i was looking for, just wanted the peace of mind that the 1/8" gap at 10" will work.

    Riaan: umm, i'm lost when it comes to metric! lol

    10" is all the space i have for the main overflow, i have a 6" return (slim), 10" main overflow, and a 6.5" emergency overflow...i'm going to go with the herbie drain

    if the 1" drain is .787 sq inches, in theory the emergency (6.5"x0.125"=0.8125), should also be able to handle all the flow a 1" drain can.


    All in all, i'm not planning on running a crazy amount of flow from my return pump anyway. i'm most likely going to be using an Eheim 1260 and at 3ft head its around (400gph or 1800 lph!), but i'd like to test the overflow with a mag 12 (1200gph), which my emergency will definatly not handle...
     
  6. lIghty

    lIghty

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    And how do you plan on securing the bulk head or if it starts to leak?

    Why not just make use of a rear exit durso or the tunze overflow?
     
  7. Mewik

    Mewik

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    Won't that design land up being pretty loud and sucking for air? I think you might need to add an air inlet pipe onto the return pipe to silence it, then that would need to extend above the water line to prevent it just spewing water out if i'm thinking correctly.

    My overflow box is quite a bit wider, 30mm x 200mm x 200mm with a 2" bulkhead. The return pump is pushing about 2200l after all the height plus I feed my reactor off the return line and the overflow is borderline on being too small, so i would guess 3mm would be too small. Flow dynamics and gear ratios are the sort of technical things that make my head spin so I might be wrong :p

    I don't know what the proper name for my overflow is, its some ghetto poorman's durso I think :blush:, but the air sucks in from the air pipe in top of the t-piece that fits onto the bulkhead, that little air pipe makes it almost silent without adding valves etc.

    [​IMG]

    [​IMG]
     
  8. Mewik

    Mewik

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    If i did it again I'd just fork out the cash on one of these scarico, overflow,

    They are damn pricey though unfortunately. Think I must start saving....need some damn glass as well then. :(
     
  9. samiam

    samiam Thread Starter

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    so i had a chance to work on my overflow this weekend, decided to make out of acrylic. I'm doing a herbie design, so it will be dead silent while running. here's a couple pics.

    [​IMG]

    [​IMG]

    so the layout is return 6"/main drain 10"/emergency drain 6.5". the emerg, is 0.5" taller than the main, so it will hopefully handle any blockage the main may have...

    I got it all plumed this weekend, but didn;t have a chance to test, as i had a couple pinhole leaks in my acrylic boxes.

    let me know what you guys think, below is the main reason for going through all this trouble! :thumbup:

    [​IMG]

    [​IMG]
     
    Last edited: 12 Mar 2012
  10. samiam

    samiam Thread Starter

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    got a chance to test the overflow!

    works great, can handle 600gph minus 3feet of head pressure :)

    only issue is that at 600gph the return into the tank creates a small wave which inturn causes a small splashing sound...might have to turn it down to keep the tank silent...or maybe add a longer "cap" to stop the wave...

    heres a few pics

    [​IMG]

    [​IMG]

    [​IMG]
     
    Last edited: 22 Mar 2012
  11. Express Reef

    Express Reef

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    cool now you have a wavebox... like the wave it makes:p
     
  12. samiam

    samiam Thread Starter

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    haha thanks, i'm liking it too!

    i'm just concerned that with the saltwater, the splashing will cause a lot of dried up salt to build up in that corner...
     
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