Flow Rate through Plumbing Pipes

Discussion in 'General Discussions and Advice' started by ChrisRaubs, 15 Jul 2012.

  1. ChrisRaubs

    ChrisRaubs

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    Hi There MASA team,

    I have come accross this formula on a website, and hope you guys can help shed light / clarity on the matter. I'm having some difficulties with the equation... :blush:

    Q = (C times A) times (the SQRT of (2 times g times H)) :eek:

    Where:

    Q = Water Outflow Volume
    C = Discharge Coefficient (0.601 for sharp edges, & 0.941 for well rounded edges)
    A = Cross Sectional Area Perpendicular to the Water Flow
    g = Gravitation Constant (9.8 meter per seconds squared)
    H = Water "Head" (Height of water surface above discarge aperture in meter)

    An example was mentioned:
    -------------------------

    If we assume a 10mm head above the 37mm diameter standpipe inside the tank, the maximum water flow through your proposed 37mm (ID?) hole, will vary between ~ 300 - 500 litres/hour (86 - 135 gallons per hour). If the "head" increased to 25.4mm (1"), the flow would increase to between ~ 500 - 800 litres/hour

    i.e

    Q = (.0941 x .032) x (the SQRT of (2 x 96.04 x 0.01)
    = (0.030112) x (the the SQRT of (1.9208))
    = 0.030112 x 1.38592929
    = 0.04173310278048 cubic meter per second, which relates to 41.7 L/s, and in turn to 2502 L/min ?

    Clearly i'm sitting the pot miss some where?

    An elaboration to this will be highly appreciated. :yeahdude:
     
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  3. Dot Dash

    Dot Dash

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    Dude, don't complicate things for yourself, use the biggest pipe that you can, that will lower the frictioin coefficient and give of the best flow that you will be able to get. Q-in will = Q-out, no matter what, but there are loads of factors that can influence the actual volume (liters per second) that come out the end of the pipe. Google Bernoulli equation, that will hep you calculate the actual flow in pipes. But do you actually have to do that? I don't think so. Just my opinion.
     
  4. ChrisRaubs

    ChrisRaubs Thread Starter

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    ... haha,,, that's the complicated me,, :blush:

    The actual reason why i would like to know is cause i haven't started my tank as yet, currently have a 22 gal fresh water tank which i would like to convert into reef... I have a return pump (which is not being used) which has a rating of 4000l/h at 0 head,,, my head will prob be about 1-1.5m reducing the rate of the pump to about 2500l/h ... I just want to double check whether even a 50mm pipe will be able to supply the volume of water required (from the DT, down into the refugium + sump set-up)

    A simple build around would be to T-off the return pipe (to the DT) and re-circulate some of the water being pumped back to the DT to the start of the refugium + sump set-up...

    If i could calculate, i don't need this work around??
     
  5. Dot Dash

    Dot Dash

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    Set up the plumbing as you would from you sump to the level of the return to you DT. Fill the sump with water and pump it into a bucket with a know volume. Record the time it takes to fill the bucket. Calculate the volume of water per hour. This way you will know what the pump is capable of. You can always add a valve to the drain to make sure you don't flod the sump.
     
  6. Manic

    Manic Moderator

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    Firstly, that pump would be way to strong for a 22 gal tank. My 250L tank only had about 2000Lph of return pump.

    Secondly, I have used a 4600Lph pump with 20mm pipe and a 50mm return. So 50mm will be more than enough.
     
  7. mariusmeyer

    mariusmeyer

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    You will be amazed at how much water gravity can pull through a 50mm pipe. I am running about 3000LPH through 2 50mm overflows and they look like they are doing nothing. Only reason for having 2 overfows is for safety reasons.
     
  8. ChrisRaubs

    ChrisRaubs Thread Starter

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    MANY thanks for all of the replies thus far! :thumbup:

    I was a bit scared that this would be the case... I guess I'll have to limit the output on the pump, and do the work around to the start of the refugium...

    This leads to another question then,,,

    Is there a general "accepted" flow rate through the refugium + sump? in my case i'm now sitting with too much flow... Would too much flow make the refugium + sump ineffective?

    Set-up Pics:

    [​IMG]
    [FONT=&quot][/FONT]
    [​IMG]

    All the input is highly appreciated!!
     
  9. Dot Dash

    Dot Dash

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    The pump that you want to use, 4000 litre with no head, might not give you what you hope at 1,0m or 1,5m. Test it to see what you get. Sound like a flow pump and not one designed to push water uphill.
     
  10. dallasg

    dallasg Moderator MASA Contributor

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    my advice is that a return pump should only be used to take water from the sump to the tank, and not be used to create flow in the DT, but some will disagree

    but what i do see is a potential knightmare with multilevel sumps, i know i have the same setup, make sure that when your return pumps stops, you lowest sump can take all the overflow from the DT and other sump. the best way around this is to make the overflow in the first sump as high as possible and the water level, so if the pump stops only a minimal amount of water flows to the bottom sump
     
  11. ChrisRaubs

    ChrisRaubs Thread Starter

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    Hi Dot Dash, it's definitely capable of pushing water uphill,, bought it initially a while ago to to service a waterfall feature,,, the pump is rated up to a 6m uphill head? To cold to leave my blanket to look at the packaging now to make sure... lol

    Hey dallasg ,

    LOL, i was thinking of using the flow from the pump to create "current / movement" in the DT... :whistling:

    I have definitely bargained for the difference, as i would have the return pump switch on/off every 15-30 mins to create feeding time in the DT... But thanks for the "heads up" !! :thumbup:
     
  12. ChrisRaubs

    ChrisRaubs Thread Starter

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    Coming back to this equation ...

    Has anyone managed to wrap their heads around this? I used excel to it's fullest extend to try and get the example answer to match my calculations...

    This is purely out of curiosity, and could probably still help other newbies which would like to know ... :biggrin:

    "sometime our minds gets stuck at the wrong detail" ;)
     
  13. dallasg

    dallasg Moderator MASA Contributor

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    :thumbup:

    i will reply to the equation in the morning, my maths brain i pack away on weekends
     
  14. Rory

    Rory Admin MASA Contributor

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    I will definitely agree there...
     
  15. RiaanP

    RiaanP Moderator

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    a 50mm downpipe can handle up to 5000L/h under gravity. Just remember to round off the edges as that would also help to increase the flow rate in.

    I'm running a split level sump. My Remote DSB plus Cryptic tank is higher than the main sump end everything flows back to the main sump.

    I'm in Centurion, so If you want to see how I did it, your welcome. But before this weekend, as the system will be broken down mostly on Saturday.
     
  16. ChrisRaubs

    ChrisRaubs Thread Starter

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    Hey there @RiaanP ,

    Thanks for the tip, I'll be sure to sand those edges nice and round... Thank you very much for the offer, I would have loved to come through but I'm swomped at the moment...

    If you're setting up another system, maybe I can through and view tht...

    Thanks again for the offer!!
     
    Last edited by a moderator: 26 Nov 2015
  17. carlosdeandrade

    carlosdeandrade

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    Sorry dude, I never did Physics in uni, and never passed it in high school.
    Ask me a Chemistry question any time!:)
     
  18. RiaanP

    RiaanP Moderator

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    Yes I am, and same concept will be there but not that clear.
     
  19. ChrisRaubs

    ChrisRaubs Thread Starter

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    Hey there Team,

    Oom Hennie pointed me into the correct direction,,, also pointed out that there was already a calculator on MASA for this very calculation required... http://www.marineaquariumsa.com/general/flowcalcs.xls

    * sHould anyone require it in future...

    Tanks alot to all the input by all members... MASA community RoCkS !! :yeahdude:
     
    Last edited: 16 Jul 2012
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