Flow over DSb

Discussion in 'Pumps and Waterflow' started by Bayls, 24 Dec 2007.

  1. Bayls

    Bayls Not often called Junior!

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    Hi
    In the simple sump I am designing, water goes from the tank overflow to a skimmer chamber, then over a DSB and into a return pump chamber (maybe with some baffles after the skimmer to reduce micro bubbles).
    I've been thinking that whatever the flow of my pump is - say 6000lph or more - this will probably be too fast a flow over the DSB. Am I correct and if so, what is the simplest design to divert some or most of the flow away from the DSB?

    Fantastic site guys - I've picked up many tips that I know would have caused me much grief if I hadn't incorporated them into my final design up front!

    Cheers, and merry Christmas to you all.
     
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  3. KevinW

    KevinW

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    What size is the sump, or more specifically, what is the surface area of your DSB and what depth of water runs over it?
     
  4. Kanga

    Kanga Retired Moderator MASA Contributor

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    Yes also what water volume is the entire system.

    I have a pump 6000L p/h on my 800L system, but after the head height, SCWD and ends I reckon its down quite a bit.

    But flow over my 1.1m x 50cm dsb is nice and gentle
     
  5. SIMS

    SIMS

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    safe question..

    Display 850l
    Sump 270l
    DSB 600x500 water is 25-30cm deep over dsb
     
  6. Bayls

    Bayls Thread Starter Not often called Junior!

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    Total volume is 650l
    The DSb is about 80 x 40. Depth of water will be about 10cm I guess.

    Cheers
     
  7. shane

    shane

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    Hi Guys,
    Does it make a big difference what size or surface area the dsb is and at what depth the water runs over the dsb?I understand that if the water flow is to fast there will be little or no reduction in NNR from the dsb.
    Cheers
     
  8. KevinW

    KevinW

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    Flow may be a bit fast but need someone with a knowledge of flow calcuations to determine what your flow works out to.

    The bigger the surface area of your DSB the greater the effectiveness. The depth of water over the DSB is of interest as this also gives an indication of flow rate (pump volume through diameter of "pipe" ((width of DSB and Depth of water)
     
  9. Kanga

    Kanga Retired Moderator MASA Contributor

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    Yes size does matter, and speed as well. MY water is 15-20cm over my DSB and like I said it a nice gentle flow.

    I dont think there is any formula that states Xl/ph over Xcm/2 at Xcm high
     
  10. lIghty

    lIghty

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    Hi Bayls, I refer you to a thread I started last night, "Water flow speed vs level" under Pumps and Waterflow, I feel it would make a difference, remembering that we are trying to change the velocity on top of the dsb and not affecting the overall water return rate.
     
  11. KevinW

    KevinW

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    Sorry missed that thread lIghty. Very interesting.
     
  12. Bayls

    Bayls Thread Starter Not often called Junior!

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    Thank you all guys! I will increase the depth of water over my DSB.

    Cheers
    (BTW, is there a link anywhere here which explains all of the commn abreviations that you experts use?)
     
  13. lIghty

    lIghty

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    Not that I know of.

    IMO-in my opinion
    DSB-Deep sand bed
    BTW- by the way.

    don't stress, you'll pick it up in no time.
     
  14. viper357

    viper357 Admin MASA Contributor

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  15. Bayls

    Bayls Thread Starter Not often called Junior!

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    Aha! Thank you very much!
     
  16. dendrosa

    dendrosa Member

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    I believe the function and operation of a dsb is often misunderstood. A dsb does not actively absorb nitrates out of the water column, no matter how fast or slow water flows over it. A dsb is actually a catalyst , it provides the correct environment for micro fauna to inhabit and thrive, hence the importance that a dsb is made up of the correct grain size. It is this microfauna which draws uneaten food, detritus etc into the sand bed as a food source where eventually the bacteria can get to work on it. Microfauna don’t feed on nitrates so putting your dsb downstream of your skimmer is defeating the point of a dsb.
     
  17. lIghty

    lIghty

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    Bayls, Read this thread as it was writen by Galibore, who has had expriance.

    DSB for beginners - Galibore
    http://www.marineaquariumsa.com/showthread.php?t=714

    Just to Quote

    "Certain anaerobic bacteria will start to thrive in this low oxygen environment. These bacteria will then start to consume Nitrate present in the water column. The product of the consumption of the Nitrate is Nitrogen which is released into the air in the form of bubbles."

    "You can keep an eye out for signs of too little flow. One such sign is the formation of Cyanobacteria on the DSB substrate."
     
  18. Bayls

    Bayls Thread Starter Not often called Junior!

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    Hi Dendrosa, are you saying that the DSB should be before the skimmer in a sump? Easy change for me to make.......

    (it's Xmas eve and people are still on a marine forum - isn't that amazing!)
     
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