Sizes and rates

Discussion in 'Beginner Discussions' started by VicZA, 31 Jul 2013.

  1. VicZA

    VicZA

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    Hi All,

    How do we work out how many litres a tank holds ? and how do we know what the flow rate (rating?) should be on the return pump to be used ?

    I am looking at a 1200 x 600 x 450 tank
     
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  3. Tiger eye

    Tiger eye

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    I don't know how to work it out, but what I have found is that different makes of pumps actual output differ from what the rating says. For example x pump is rated 3000 l/h and will empty a 25 litre drum in 1min and y pump will empty the same drum in 40 sec but is also rated 3000 l/h.
     
  4. dallasg

    dallasg Moderator MASA Contributor

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    Volume is length x breadth x water height all in mm divided by 1 000 000

    1200x600x 400 = 288L
     
  5. RiaanP

    RiaanP Moderator

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    how wide is your sump (front to back)?
    And how wide is your overflow chamber?

    Total length of overflow chamber must be taken into account. Wide overflow can handle a lot more water than a narrow overflow. Well narrow can handle the same volume, but at a big increase in head height. Flushing smaller fish over far too easily.
     
    Last edited: 1 Aug 2013
  6. VicZA

    VicZA Thread Starter

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    Ok, cool so my tank will be a 300l tank with a skinny coast-to-coast overflow. Sump will be 700x400x300(water hight) so thats another 80l. So what rating should the return pump be? 2000l/h, 3000l/h
     
  7. belindamotion

    belindamotion Google Master

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    I'm no expert but I'm sure I read that you'r return pump is usually ..roughly 10x the total volume.. I'm sure someone will correct me if I'm wrong...:blush:
     
  8. RiaanP

    RiaanP Moderator

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    depends if your overflow can handle that.
    300mm wide overflow with 10mm head and you look at a pump that delivers 2000L/h into your display. NOTE, not a pump rated at 2000L/h. But delivers 2000L/h after head height and back pressure are taken into account.
     
  9. VicZA

    VicZA Thread Starter

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    OK, so what does that mean then ? The overflow will be about 15mm wide and run the full 1200mm length - can that handle it ? Not sure what you mean by handling .... please explain.
     
  10. RiaanP

    RiaanP Moderator

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    Like a normal dam.

    Weir height, or water head height, is the distance between the weir surface, or dam wall concrete and the actual water surface as it is going over the wall. The depth of the water running over.

    If it rains a lot, then you have a lot of water coming down via the rivers feeding the dam. And then when it starts to overflow, the height of the water running over the overflow will increase, as more and more water enters the dam. There needs to be a maximum relation between what can enter the dam in case of heavy rains, and the water the dam can discharge, without damaging the dam wall or surroundings. 10 meter high water running over the dam wall is an engineering failure. Dam needed a wider overflow, more gates to allow water out with an acceptable head height.

    Now, put that into your display.
    If you pump 10000 L/h into your display, but your overflow is only 200mm wide. That means that the water as measured on top of the overflow up to the actual water level, your head height, would be 40mm That is enough to be very noisy, flush all fish over, most likely touching your bracing, or even flooding your display tank. You are pumping more water in as what it can let out.

    By the way, on a overflow width of 1200mm with same 10000L/h pump, the head height drops to 12mm. A lot better. Ideal would be between 3 to 4mm, so that would be a pump that delivers between 1400 and 2100L/h into your system.

    Also take into account, that the water head is the water that will go down to your sump EXTRA, in case of a power outage. So the less the head, the less extra buffer space you need in your sump. A 4mm head height and that is 2.88L water. 10mm head height and its 7.2L water. As on your system with footprint of 1200 by 600mm.
     
  11. VicZA

    VicZA Thread Starter

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    AWESOME ! Thanks for the thorough explanation - much appreciated
     
  12. RiaanP

    RiaanP Moderator

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    Pleasure
     
  13. pkc

    pkc

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    There is something else not covered.
    To work out your return pumps actual volume to the aquarium, you put the return pump in a bucket of your salt water with the return hose attached that you intend on using and hold it at the aquariums height.
    Hold the end over another bucket and run it into that bucket for 15 seconds.
    To measure the actual water amount returning to your aquarium, put the buckets content into a measuring jug and multiply what was in your bucket by 4.
    That is what your return pump is running at.
    We always work on return water running back at around 5 times the entire water volume per hour and the in tank wave makers or just pump made current, at 20 to 25 times the in tank water volume per hour.
     
    Last edited: 2 Aug 2013
  14. viper357

    viper357 Admin MASA Contributor

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