slim overflow box

Discussion in 'Pumps and Waterflow' started by Difficult marine, 14 Nov 2013.

  1. Difficult marine

    Difficult marine

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    I am going to make 600 to 800l tank. Can the slim overflow handle the 10000l return pump? anyone have experience to tell. from the pump to the display about 1.8m high.
     
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  3. RiaanP

    RiaanP Moderator

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    make it as wide as possible.
    Too narrow and you will end up with a lot of water head in the display.

    What is the distance between overflow top and the rim of the tank, or the underside of the euro bracing?

    Do you want to use overflow comb / teeth?
     
  4. Difficult marine

    Difficult marine Thread Starter

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    what is normal wide for the slim overflow?
    when the water fall ,did make noise?
    what is your suggestion for the wide for 10000l return pump?
    I can use overflow comb,is it slow down the water and water head increase?
     
  5. Christo

    Christo

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    Well I have a 900l System! My Tank is 1850 x 750 x 650! My overflow streches about 1200 at the back! Have a 2 Sicce M5800 Return pumps, only running only 1 at the moment. So it's 5800l Return (without head higth) have about 10mm level gain in the Display! Thats with an Overflow Comb!
     
  6. Visser

    Visser MASA Contributor

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    @Difficult marine, i have an overflow calculator spreadsheet that I compiled a while ago to calculate required flows over a certain length / width overflow.
    Will try upload it tomorrow if I get a couple minutes free time.
    For a tank that volume, & that flow rate, I would go for a 12-16mm width on the skinny overflow.
    Overflow part to be +-1m with the return at +-150-200mm long.
    Just make sure you have a "cover plate" glued on top of the return section to prevent the water from blasting straight up & out the tank...
    Make the "cover plate" to have an overhang of 25mm in the tank direction...(will help direct return flow into tank)
     
    Last edited by a moderator: 26 Nov 2015
  7. Difficult marine

    Difficult marine Thread Starter

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    Hi Christo and Visser

    Did they making noise when the water fall? this is my main concern.

    Now only slow return can make it work but I am worry too slow will make display and sump have temperature different........Is it correct?
     
  8. RiaanP

    RiaanP Moderator

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    using
    Q = 1.84(L – 0.2H)**(H3/2)
    that means your overflow needs to be 1500mm long for a 10mm head height.
    For a delivery rating of 10000L/h.
     
    Last edited: 15 Nov 2013
  9. Visser

    Visser MASA Contributor

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    You can still keep the high volume return pump & have a silent overflow.
    Secret is to install a strainer valve on the main overflow pipe to allow the water level to rise slightly in the overflow chamber. This will cause the overflow to be dead silent!
    Then, in case the main overflow gets blocked, you should have an emergency overflow pipe as well.

    Will try to draw a diagram of how it works & upload now...
     
  10. jclaas

    jclaas

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    Can you please provide names for the letter notations used in that formula?
     
  11. RiaanP

    RiaanP Moderator

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    Q is the water flow rate in m3/sec,
    L is the length of the overflow in m
    H is the head over the overflow in m

    Sorry, formula is setup for dams and water causeways. So it works in meters
     
  12. Visser

    Visser MASA Contributor

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    This is more or less what it looks like.
    Ive designed 3 tanks like this for friends / fellow reefers & they work wonders!
    [​IMG]
     
  13. Visser

    Visser MASA Contributor

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    Sorry, double post
     
    Last edited: 15 Nov 2013
  14. Visser

    Visser MASA Contributor

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    Feel free to send me a pm if you dont understand it & I will send you a 3d model drawing...
     
  15. 2balive

    2balive

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    Will this formula work for a 3 sided overflow?

    Can I use this formula for a three sided overflow and just add the sides together to get to the length?

    If I add teeth, will it increase or decrease the H and Q?
     
  16. Visser

    Visser MASA Contributor

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    You cant use that formula if you are going to use a overflow comb. (changes all the factors.)

    For overflow combs, you have to use critical flow calculations as the backpressures caused by each comb becomes a factor.

    Width of each comb,width of gaps between combs, thickness of comb, profile etc all comes into play.


    Anyway. Yes, you can use the formula for 3 sided overflows. Just add the 3 lengths to use in the calculation.

    If you add a comb, the overflow height will +- double... (depending on above factors)
     
  17. RiaanP

    RiaanP Moderator

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    Yes you can. The inner length of the box.

    With teeth, Q stays the same, You are not changing the return pump, so you still got the same volume of water entering the display and that should be equal to the flow over the outlet. Else display will flood. The H will increase. And if not enough head height you can end up with water touching euro bracing, or again flooding the display. Been there. Done that. Got the wet towels.

    Not sure as to what the formula must change for the teeth. As they are obvious obstructions in regards to flow.

    But for the lazy to understand that formula. Its roughly works out for a head (H) of 10mm, that for every 150mm (L) overflow you get another 1000L/h water (Q)

    Double the H and you almost triple Q
     
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