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Thread: gravity filter

  1. #1
    Nisai
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    Dec 2010
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    gravity filter

    I am finally doing a upgrade to my Koi pond. Im going to make it deeper and put a bottom drain in it. Im good on all of that work but I am having issues with the concept on these gravity filter design. I plan on placing a vortex settling tank, a bio filter, and a mech filter. I want it to end up going to 1 waterfall and 1 bog filter behind the pond. The issue Im having trouble with is everything I keep reading is saying to place the pump at the end of the line so you dont chop up everything your trying to take out and you get better debris/trash removal. So would all of my tanks and filter have to be pressurized? Or would the pump be after the filters but before the bog and waterfall? Does the filter set-up have to be above or below the pond to work properly? I havent been able to SEE enough information to help me with my own design. figured I would let u pros give me a few pointers.

  2. #2
    Honmei ricshaw's Avatar
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    Quote Originally Posted by hulsey View Post
    I am finally doing a upgrade to my Koi pond. Im going to make it deeper and put a bottom drain in it. Im good on all of that work but I am having issues with the concept on these gravity filter design. I plan on placing a vortex settling tank, a bio filter, and a mech filter. I want it to end up going to 1 waterfall and 1 bog filter behind the pond. The issue Im having trouble with is everything I keep reading is saying to place the pump at the end of the line so you dont chop up everything your trying to take out and you get better debris/trash removal. So would all of my tanks and filter have to be pressurized? Or would the pump be after the filters but before the bog and waterfall? Does the filter set-up have to be above or below the pond to work properly? I havent been able to SEE enough information to help me with my own design. figured I would let u pros give me a few pointers.
    With a gravity system it depends on which parts of the filtration system have to be pressurized. For example; a vortex settling tank is not pressurized, a bead filter is usually a pressurized filter.

    Visualize, from left to right, the following parts ALL below ground level with the water level about 6 inches above ground level:
    The pond -> vortex settling tank -> open mechanical filter box -> open bio-filter box.

    The pond would have a pipe going to the vortex settling tank which would have a pipe going to the open mechanical filter box which would have a pipe going to the open bio-filter box which would have a pipe going to the pump which would go to the bog and water fall.

    One of the problems some people have with ponds and filter tanks buried in the ground is how do you drain them from the bottom. They think that for a drain connected to a bottom of lets say a 36" tall vortex settling tank that the drain pipe and valve must be at the same level as the bottom.
    Actually, with gravity systems, the drain outlet only needs to be below the normal water level. In the case of a vortex settling tank buried in the ground, the bottom of the settling tank may be 36" down with a drain pipe coming up to 6" below ground level with a valve connected to a drain pipe. When the valve is opened the water will drain from the bottom of the settling tank and if left open will drain until the water level in the pond (and the rest of the gravity system) drops to the level of the valve outlet.

    Hope this clears your issues with gravity system designs.

  3. #3
    Nisai
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    filter understanding

    well I dont think Ill have a problem draining any of them from the lay of my yard. If I was able to draw it out in how im thinking of making it could you give me some corrections and pointers?

  4. #4
    Honmei ricshaw's Avatar
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    Quote Originally Posted by hulsey View Post
    well I dont think Ill have a problem draining any of them from the lay of my yard. If I was able to draw it out in how im thinking of making it could you give me some corrections and pointers?
    Sure.

    Draw a diagram. Save it as a jpg on a photo sharing web site. Use the Koi-Bito messages "Inset Image" tab to upload.

  5. #5
    WAC
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    Tosai
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    Hopefully these diagrams will help clarify a bit.

    When all the tanks are below grade & connected, water can be drawn from the tank furthest away from the pond.


    Subsequently a % of "draw down" will occur starting w/the tank closest to the pump which causes the influx of water from each tank before it. The final draw occurs from the bottom drain(s). Common factors dictating the amount of draw down that occurs include:
    • size of pump
    • size of tanks
    • media chosen
    • size of pipe
    This same concept of gravity fed tanks in-series can work with a submersible or an external pump.

    Everything after the pump is considered "pump fed". A pressurized filter must be pump-fed but can be situated below grade or above grade.
    Attached Thumbnails Attached Thumbnails gravity filter-gravity-w-submersible-04.29.11.jpg   gravity filter-gravity-w-external-04.29.11.jpg  

  6. #6
    Nisai
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    (still working on the drawing, have it done in a few hours) one thing im still kind of confused about. The pump is pulling from the last tank. this concept messes with me. example} you have some leaves by the bottom drain. of course if your filter is down by the level of the pond the water will be pushed to keep the 2 equal thru the piping to the drain but is the push enough to move leaves and debris thru the piping? Is it as strong as the suction of the pump? My whole reserve is I dont want to put too small piping or small a pump into this system only to have to change it later. hopefully after I get this drawing done you guys can help me out with some numbers.

  7. #7
    WAC
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    Yes ... essentially for every "drop" of water the pump is pushing onwards ... a drop of water is being filled into the tank. This chain reaction is why you see the "draw down" effect.

    So as you mentioned, the strength of the pump essentially (more or less) translates all the way down the chain to the bottom drain. This is why proper pipe sizing is important.

    Too small a diameter & you'll have way too much draw down & too large of a diameter you'll have way too little velocity & debris may settle in the pipe work itself.

    The pump is pulling from the last tank. Now each tank is nothing more than an "extension" of the pond itself.

  8. #8
    Nisai
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    I want to follow along. don't mind me...

  9. #9
    Nisai
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    pond layout | Flickr - Photo Sharing!

    Quote Originally Posted by ricshaw View Post
    Sure.

    Draw a diagram. Save it as a jpg on a photo sharing web site. Use the Koi-Bito messages "Inset Image" tab to upload.


  10. #10
    Nisai
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    this is what the poor guys were having to deal with and why I have to fix it. The owners before built the walls of the pond with stacked brick then slapped a thin layer of concrete over it....needless to say over the years this pond has some leaks.

    koi pond | Flickr - Photo Sharing!

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