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I have looked through all the autodosing threads I can find and all require electricity. Has anybody built one that doesnt require any power other then gravity. Would it be possible to just use standard lab apparatus to stage a couple of 1000ml seperatory funnels above a tank with a suitably low drip rate to equal a daily dose. Other then clogging, why would this not work. I realize it might look unappealing to some but I would find it sort of attractive in an apothecary window sort of way.
 

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I think this is an interesting idea. I think it could look attractive in a weird way. Can you get the lab parts on ebay I wonder?

I have looked through all the autodosing threads I can find and all require electricity. Has anybody built one that doesnt require any power other then gravity. Would it be possible to just use standard lab apparatus to stage a couple of 1000ml seperatory funnels above a tank with a suitably low drip rate to equal a daily dose. Other then clogging, why would this not work. I realize it might look unappealing to some but I would find it sort of attractive in an apothecary window sort of way.
 

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A gravity drip system is exactly what the medics use for adding fluid to the blood system. Why not adapt it for a drip system to apply your ferts to the tank. :icon_smil
 

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Discussion Starter · #7 ·
I have read that iv drips are not that accurate over longer periods of time, and that is why I was thinking of a seperatory funnel instead. Plus sep funnels look way cooler and sciencier.
 

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Burettes are meant for titrations, and are thus very accurate. You probably don't want to spend that much money on one, however. Not to mention it is acrylic and not glass too...

A separatory funnel is probably the way to go.
 

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There are a few drawbacks to a gravity fed system.

You realistically are limited to the head provided during the dosing. If you do a nonstop drip, you need to account for the fact that as time progresses, and the reservoir drops, the flowrate will recede (and not proportionally, but expenetially). In other words, if the reservoir has 1 foot of liquid height one day and 6 inches the next, the flow WILL be different, thus the concentration of the dosage is off. This could be remedied by doing a highly dilluted solution.

So if you attempt to set up a system for a month dosing cycle, the concentration of dosing in the beginning of the month would be alot higher than at the end (assuming that the solution remains suspended and is does not settle).

Another way to avoid that head issue is to use a really flat container (which in essence provides limited height change) But this may not be practical and may just be plain silly.

Gravity, although convenient, does not provide a consistent result, but if you can set it up with a really diluted solution that doses over a very long time frame, you may be able to limit the variability of the concentration (something like you get 2 ppm of KNO3 at the beginning of a week, but by the end of the week its dosing 1.75 ppm).

Obviously, you need to test your system for volume per dosing time and set yourself up a chart to establish how you set the concentrations to the time.

But be diligent in looking for clogging or deteriorating dosing volumes over time!

Personally... I find this to be more work than its worth. But my hats off to you if you think its more convenient or worth a try.
 

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Don't forget the effect of evaporation. If the drip rate is low, each drop can partially evaporate as it forms. Then if the concentration of fertilizer salts is near the saturation limit of the solution being dripped, salts will come out of solution, and that would lead to growth of salt crystals where the drops start. Keeping the "drop" under the tank water surface would solve that, but introduce other problems.
 
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