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Thread: Air Lifts? I would like to learn more.

  1. #1
    Oyagoi CarolinaGirl's Avatar
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    Air Lifts? I would like to learn more.

    I am seriously considering using air lifts for my new pond. I have found loads of information on the web about them, but am having trouble understanding what I am reading. Assuming a 4" drain line can pull 3500 gph, how many water return lines (and of what size) will I need? How far down in the water return line is the air introduced? How much air is needed? I think in these times of rising energy costs, air lifts might be the way to go. They have been used in aquaculture for years and I am sure that industry used them for the energy savings. Any air lift experts out there? thanks!!

  2. #2
    Oyagoi CarolinaGirl's Avatar
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    I found some calculations on the web. Math is not my strong suite though. Here's the rough formula. So if I convert the pipe length and diameter to inches and assume 2" return pipes with a 48" lift, my formula looks like this:

    Q=((.758*.9259*4.8798)+.01196)*35.719
    so Q = 122.7576 liters of water per minute, which works out to 1944 gph??? Is that even possible? I think based on the last part of the equation below, if I am moving 122.8 lpm, I need 9.8 liters of air per minute for this to function properly. Someone who's better in math than me.....please check my match for me??

    2" pipe = 7.62 cm pipe
    48" lift = 121.92 cm of lift


    Maximum water flow from an airlift pump
    Limitations of calculation (out with these parameters the calculations will become less accurate):
    Pipe diameter 1.5 - 8cm
    Pipe length 60 - 300 cm

    Q = ((0.758 x (%s)1.5 x ht0.33) + 0.01196) x d2.2

    Where ;
    Q=Water flow rate, litres per minute
    ht=Total length of pipe (cm)
    d=diameter of pipe (cm)
    %s=Percent of pipe under water (measured from point of diffuser to discharge)

    Air requirements for optimal water flow are typically 8-9% of the water volume. Above 10%, normal bubble flow ceases and the efficiency of the airlift drops rapidly

    edit....some of the parts of that formula did not post properly.....here's the link.....

    Airlift

  3. #3
    Oyagoi
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    Not sure about all those calculations....but I've run a few airlifts in my day.

    Number one, an air lift sure ain;t gonna work with four feet of TDH (Total Dynamic Head). Air lifts work very well, but not in applications requiring the water be lifted more than six inches. Three inches of lift much better yet.

    If you want to move water from one container to the next with an air lift, you need the two containers to be almost equal with respect to the elevation of the top of the water from one tank to the next. Lifting one or two inches, you can;t beat an airlift for effeciency. Lifting more than 6 or 8 inches, you are going to be better off with something like an axial flow (low head) pump.

    We built some ten horsepower airlifts many years ago. Ten horsepower regenerative blowers and one inch diameter open air discharge (about two feet down) into 12 inch lift pipe. Our lift was (TDH) was a tad over one inch. The rig moved huge amounts of water for only ten horses.

    Brett
    Brett

  4. #4
    Oyagoi CarolinaGirl's Avatar
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    Thanks Brett. The 48" of lift is not from the surface of the water, it's the point where the air is injected into the return line, 48" deep. I only want to return the water about 2" above the water surface. Sorry I didn't explain that very well.

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    Oyagoi kntry's Avatar
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    Cindy, I emailed Kent last week about this. I'm hoping he'll post some info on it.

    Brett, if I have 4" pipe running horizontally from a shower collection chamber to an above ground pond with the pipe resting on the side of the pond and elbowed down into the pond for the return water, would this work? The water wouldn't have to be lifted, just pushed forward.

  6. #6
    Sansai
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    What type of circuit do you want to use it on and how much flow do you need. You girls are really determined. Yeah that's a good word for it. I got about 3600 gph with a 100 lpm Medo pump at about 1.7 amps I believe. Aeration plus water movement with a 3 inch pipe and about 6 inches of lift.

  7. #7
    Oyagoi Sangreaal's Avatar
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    Considering an air lift system myself here, Cindy. Sounds really easy to build and the best part is the economy of it all. Still researching, so I hope more brains chime in here with more info...

  8. #8
    Oyagoi bekko's Avatar
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    CG, I got about the same answer, 132 liters/min = 2100 gph.

    If you want to save more energy, increase the pipe diameter and decrease the depth of the diffuser. A three-inch pipe with the diffuser at 26 inches deep will move the same amount of water. It takes a lot more energy to pump air down to 48 inches deep. Also, with a shallow diffuser you can use a regenerative blower which puts out a lot of air at low pressure for not much electricity. There is a table with specs in the Aquatic Ecosystem catalog for Sweetwater blowers. Compare the amp draw and air flow to your piston air pump.

    The multi-compartment filters like what Waddington describes in his book are perfect for driving with air lifts. There is almost no head to contend with. Pressurized filters (e.g. bead filters) and showers which sit above the grade of the pond are energy hogs.

    -steve

  9. #9
    Oyagoi CarolinaGirl's Avatar
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    Quote Originally Posted by kent wallace View Post
    What type of circuit do you want to use it on and how much flow do you need. You girls are really determined. Yeah that's a good word for it. I got about 3600 gph with a 100 lpm Medo pump at about 1.7 amps I believe. Aeration plus water movement with a 3 inch pipe and about 6 inches of lift.
    yep....we are determined, aren't we??

    the new pond is going to be around 9000. Each bottom drain will go to a static and fluidized kaldnes filter and then I want to use air lifts to get it back to the pond. The water will only be lifted maybe 3" at the most, right above the surface of the pond. I'd like to use the Dolphin AV150 which will provide 150 liters per minute at 100 watts. They are only $128 so I can easily afford to use one on each drain. So what I need to figure out is how I can get 3500 gph from each filter back to the pond. The pond will be 7' deep, so I can inject the air into the line at any depth. The distance between the filters and the pond is only a few feet...6' at the most.

    The rest of the filtration will come from two skimmers that feed a large shower filter. I'll have to use a pump on that one.

    For Marie....here's some airlift links I have saved...they are pretty good!

    Air Lifts
    AIRLIFT PUMPS -- PERFORMANCE & DESIGN
    Airlift Pumps in Recirculating Systems

    thanks for the input Steve. I'll check aquatic eco's catalog out. This is just a lot to figure out, but I think it's really the most economical way to move water.

  10. #10
    Oyagoi kntry's Avatar
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    Kent, did you expect anything else? Cindy and I have been talking about air lifts for months. You didn't know what you were getting yourself into when you brought it up at the seminar, did ya?

    If I remember right, you used a 1/2" cpvc pipe to inject the air. Right?

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