What is the correct return flowrate?

Discussion in 'Pumps and Waterflow' started by williet, 28 Dec 2011.

  1. williet

    williet Look at the shiny LEDs!!!

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    Hi All

    I am Starting a thread to answer an interesting question. I think some of you may have thought of the question - What are other people's tank volumes what return pump are they using and what is its flow rate ?

    I will start

    Display Tank volume: 650l
    Sump: 400L
    Return pump: Rio Hyperflow HF20 (Rated 5400 with head height get 3760)


    Anyone else ???
     
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  3. RiaanP

    RiaanP Moderator

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    It depends entirely on the sump width.

    1.5 times turnover on a sump that is 300mm wide will give a completely different flow rate than a sump that is 600mm wide.

    This old rule, is most likely the cause of a lot of the guys with bigger tanks and sumps, getting detritus settlement on top of the DSB. Then proclaim that DSB in general do not work.

    If I do have this formula correct
    Q = 1.84(L – 0.2H)H3/2

    Then for a head height of 10mm over the divider, you need for different sump width:
    300 - 2000L/h
    450 - 3000L/h
    600 - 4000L/h


    That is water delivered at the top of your return line.
    That formula gives you the cubic litre per second flow rate.
     
  4. RiaanP

    RiaanP Moderator

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    williet, how wide is your sump?
     
  5. Kunhardt

    Kunhardt

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    I always thought it had more to do with the size of your return chamber?
    Posted via Mobile Device
     
  6. RiaanP

    RiaanP Moderator

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    Yes, return chamber should be big enough so that you do not suck it dry. Especially if your ATU decided to stop working. So in a way its related.

    The stronger the pump, the more water head you will have in your display. The more water will drain to sump when power goes out. And sump return chamber should handle that. I use the full sump as buffer when the power goes out.

    On previous setup with sump 650mm wide, one 3000Lh return pump left me with too much settlement on the DSB. Adding another 3000L/h pump and the problem was sorted.

    The rate of flow, is directly dependant on the width of the sump. Same volume of water being moved, but not the same flow rate. Like a wide river and a narrow gorge. Same amount of water and one is a leisure canoe trip with missus. Other an extreme red bull kayak event.
     
  7. williet

    williet Thread Starter Look at the shiny LEDs!!!

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    Hi Riaan

    Best season's greetings ! I have gone and measured, my sump sits at 580mm

    Do you need anything else ?
     
  8. RiaanP

    RiaanP Moderator

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    Well 580, use the 600mm wide.

    Then at least a pump that delivers 4000L/h after taking lift and back pressure into account
     
  9. williet

    williet Thread Starter Look at the shiny LEDs!!!

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    hmmm not quite happening. I have a pump that does 3750 ? I have another 1800 recirculating water from the return chamber back to the chamber before the DSB ?
     
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  10. RiaanP

    RiaanP Moderator

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    ok, together it should be ok

    What is the water head. The heigh of your water over the divide. That few millimetres between the top of the last divider and the actual water surface.
     
  11. Hammerhead

    Hammerhead

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    Hi Guys was busy searching the forum for return pump calculations and stumbled accross this one.

    Im in need of a return pump for my tank and intend running a DSB my Display is 1300 x 650 x 600(h) and my sump is 1200 x 550 x 450 (h) after removing the skimmer chamber and return chamber i'm left with a DSB chamber of 750 x 550 (w).

    Ive been to a LFS who advised I should go for a minimum of a 5000 lt/h return and gave me a few options.

    Syncra Silent 5000 lt/h
    Sicce Multi 5800 lt/h
    Halea 5580 lt/h
    Water Blaster 5200lt/h

    Id like to know which is the better (silent) pump, that will achieve a 10mm head height over my dividers or should I up it one size bigger? (This is a long shot).

    Are there other return pump options I should look at?
     
  12. RiaanP

    RiaanP Moderator

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    first, check the wattage used on each pump, then look at the price. I'm using a Water Blaster HY5000, on a 450mm wide sump.

    Just ensure that your overflow can handle that flow. Basically your overflow nett length must be the same or longer than your sump width. If it is the same, your display will have the same head height above the overflow glass than your sump divider. Smaller and you will get bigger head heights that will suck smaller fish over. And using a comb will just make it bigger.
     
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  13. Hammerhead

    Hammerhead

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    Hi, my overflow is a c2c along the back end of the tank using the bean overflow, i do have the rendancy fitted in as well if the 2 overflows clog for any reason, the over flow box is roughly 100mm wide and 100mm deep. If the upturned elbow is too low i could add a piece of pvc to increase the height.

    [​IMG]

    [​IMG]
     
    Last edited: 19 Apr 2012
  14. Reefhead

    Reefhead

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    I personally think it has to do with what type of filtration you are running
     
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  15. dallasg

    dallasg Moderator MASA Contributor

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    yes i agree, everything should be based on what filtration you are running, from DSB to reactors etc.
    when i ran a dsb i had a slow return pump, but used a smaller pump to flow back to the first chamber etc.
     
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  16. Reefhead

    Reefhead

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    Currently I am using NP Pellets and Skimmer in my sump and my flow is about 4 times faster through the sump then it was when I had a DSB
     
  17. butcherman

    butcherman Moderator MASA Contributor

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    I also do this
     
  18. RiaanP

    RiaanP Moderator

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    I used to have 3 pumps in my return chamber. Now I have one Water Blaster 5000L/h.

    Together the 3 pumps used a lot more wattage than the 65W Water Blaster. Water Blaster is not cheap, but I believe it does pay for itself in the long run.
     
    Last edited: 19 Apr 2012
  19. mupwi

    mupwi

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    Another thing to look at on this subject is your heating and cooling. Last winter my display tank was realy cold but the sump was a tosty 26 deg and the heaters were hardly on just because of too litle flow and too much heat being lost from the display at that stage my overflow couldent handel any moreflow so I ended up having to move one of the heaters to the display kinda defeeting the reason for the sump
     
  20. Hammerhead

    Hammerhead

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    Syncra Silent 5000 lt/h = 105w
    Sicce Multi 5800 lt/h = 90w
    Halea 5580 lt/h = 200w
    Water Blaster 5200lt/h = 60w

    the water blaster (HY 7000 /6800 l/h = 88 w I think id rather go for this one incase i need to T off for a scrubber.
     
    Last edited: 20 Apr 2012
  21. SeanH

    SeanH

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    OK i am not dumb in the literal sense LOL but reading this KIND OF makes sense. However, I am going to probably build my own tank - have done this before though things have changed now - so it would be good to find a thread or site that can say "OK Bob, so you want a tank 900x600x600 that means you will nead a sump AxBxC with 4 chambers for XY and Z and head height or return height for water is 1600 then your pump must be spec'd like "CDE" and pipe sizes must be 10mm.

    I think you get what i mean LOL - I would be happy to build a dynamic spread sheet which takes ALL the variables into account and with changing a few parameters recalculates all the requirements for specicif size tanks :)

    Just point me in the right direction lol
     
    Last edited: 20 Apr 2012
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