Experimenting with this principle for fert injection, thoughts? - The Planted Tank Forum
 
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post #1 of 8 (permalink) Old 01-25-2008, 12:51 AM Thread Starter
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Experimenting with this principle for fert injection, thoughts?

I've finally been doing the plumbing for my new project and I've been experimenting with a powerless/pumpless fertilizer injection technique using a venturi type fitting usually utilized in car washes.

The fitting accellerates the flow through it creation a venturi that draws fluid from a reservoir (ie ferts). They're adjustable via port reducers, meterting screws and another set of reducers in the inlet line.



http://www.demaeng.com/product.php?id=75&catid=28

http://www.demaeng.com/getFile.php?id=166&type=document

The info is here and I'm darn sure they're going to work. I've screwed up and ordered an inferior version (http://www.demaeng.com/product.php?id=59&catid=27) that I think will still work. Having said that, I've been testing with them in different mounting positions and they're working well, the problem is with the model I've chosen they have a relief port that without a check valve in the inlet line they can give a spurt out of.

I've put the unit inline with my water change equipment so when I introduce new water I'm introducing new fertilizer, you could also choose to control the flow with a solenoid, thus introducing fertilizer on a regular schedule.

I think its pretty cool, no pumps not bs, just plumb it inline and go, nothing to break down. The inlet lines come with a plastic screen holder that would block anything granular from plugging the venturi.

These guys had really good prices on this stuff:
http://kimsupply.com/
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post #2 of 8 (permalink) Old 01-25-2008, 04:24 PM
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Simply using a small solenoid and timer can add a specific amount per unit time.
Example, a drip gravity fed system where you can measure the faster 10 minute or 15 min dosing than you can adjust a drip for all day.

Generally, the 15 minute time is more consistent than an all day drip etc.

Consistency and reliability are two issues with autodosing.
They make automatic feeding for fish.

I'm not sure why feeding fish is less of a chore than dosing ferts, which is a but like feeding plants.

If you do one daily, or every other day etc may as well do the other.
You can do the same thing for water changes as well, solenoid + float switch to drain and fill(carbon filter removes the tap water stuff).

Regards,
Tom Barr




Regards,
Tom Barr
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post #3 of 8 (permalink) Old 01-25-2008, 09:43 PM Thread Starter
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Thanks for the comment Tom, agreed here that the consistency would be important so you'd want to ensure that the flow rate going through the device was constant otherwise your delivery of ferts wouldn't be.

In either system you'd need a solenoid, if fed by gravity as you're suggesting you need to be able to stop the system. And the way I'm applying this you need a solenoid to stop the flow of the inlet water (as well as a floatswitch).

In my case I'm automating tank fills and drains so there's no cost other than the device (fairly inexpensive). Having said all that, most people can't feed their ferts via a drip/gravity in a show tank. For a rack of tanks for something I agree 100%, gravity would be the most elegant, cheapest constant.
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post #4 of 8 (permalink) Old 01-25-2008, 10:52 PM
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Do not get me wrong, I like the idea, it's a good one.

Regrads,
Tom Barr




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Tom Barr
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post #5 of 8 (permalink) Old 01-26-2008, 05:41 AM
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I thought about this a bit also. Look like it's a good idea, price is pretty good to not to give it a try. I'm not sure how strong the suction is, but instead of a solenoid, maybe you could try the aqua lifter pump. That may produce a more consistent result as your flow rate maybe slow by filter clogging up and such.

Do you have a link to the correct unit from kim supply. That website very hard to navigate and find the correct item.


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post #6 of 8 (permalink) Old 01-26-2008, 06:22 AM Thread Starter
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I don't have a direct link, I've emailed them for pricing on the unit I'd mentioned in my post. I'll update the board once I've seen the answer.

The 'strength' of the suction is adjustable and varies proportional to the flow going through the unit, in short the ratio of delivery is basically whatever you want it to be, if I remember right all the way from 1:20 to 1:1000. The issue is testing the variability of the unit, you'd definitely want the flow through the unit to be relatively constant or else your fert delivery would vary.

I did some test on mounting orientation on the ones I bought, they varied about 20%, I've yet to do the testing with them insitu under my tank but I've no reason to believe things will change. At first I'm going to run a series of tests to ensure there's constant delivery of solution each time the tank refills.

I calculated out the ratios to ensure that it would work before I bought them, basically at the limits of precipitation the ratio was about 1:700, so we'd want to shoot for a 1:350 or so.

Regarding clogging, they come with a very fine screen on the end of the tubing so I'd venture to say they're no more susceptible to clogging than an aqualifter.
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post #7 of 8 (permalink) Old 01-26-2008, 07:11 AM
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I was thinking of hooking the aqualifter with this device, instead of simply relying on the venturi suction. Maybe you can turn it down to 1:20 when using with aqualifter. I guess I'll try it myself once my system is in place.


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post #8 of 8 (permalink) Old 01-26-2008, 04:58 PM Thread Starter
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I don't think you'd want the ratio to be any higher than necessary, it would mean your reservoir for ferts would have to be huge.

The venturi is strong and will always create a vacuum by design, if you had the aqualifter in place the unit would probably just draw the ferts through the lifter even when it wasn't on. If you've an aqualifter you probably have this problem licked, from what I can gather you'd be duplicating effort.
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