# Cheap DIY liquid doser



## scolley (Apr 4, 2004)

josh - welcome to PT! And what a brilliant first post! Affordable, reliable, autodosing would be a real boon to this hobby IMO, and I think this is a great contribution!:thumbsup: 

As you have probably seen, a number of people are working on this problem here. But I'm not sure if they have the accuracy you are talking about. It would seem that your only drawback is the reduction in fluid pumped as the holding tank level drops.

Have you thought about drilling a hole in the holding tank, then using some timed mechanism to top it off daily, so the level stays constant? I know that adds complexity and cost. Just my 2 cents.

But either way, welcome! And thanks for a great first post!


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## jasonh (Oct 26, 2003)

I had to read this a couple times to figure out what exactly is going on here... But it does make sense and sounds like a good idea. One idea I have to alleviate the problem of the reduction of the fluid - How about using a plastic container, and drill the side of it near the bottom of the container for one of those airline bulkheads? that way, ALL of the tubing is submerged, and it wouldn't matter till the container was near empty. 

May have to try something like this when I get the 125 set up, since I won't be dosing only Flourish in that tank....


EDIT: Crap, now that I think about it, I'm not sure that would work. Seeing as how any tube that is uder the water level will get filled, that's a no go. Unless of course you used a 2nd air pump in a similar fashion on the other side running at all times that the pumping air pump isn't on just to keep enough pressure to keep the liquid back...the remainder of the ir could go wherever you please....ah hell, I'm just rambling now....


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## toofazt (Jun 18, 2005)

I think this might be the simplest auto dosing setup I have seen :thumbsup:


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## josh_simonson (Mar 2, 2006)

*Well*

One could always make the vertical tubes with very thin tubing. Perhaps get 1mm ID tubing and use that for the vertical parts, then use wider tubing for the coil at the bottom. That'd get down to the point where the difference in output due to depth was negligible.

There's not much bother in topping it off once and a while. Once a month sure beats once a day! :wink: Also by topping it off, you won't shock the tank with a change in your pmdd recipe.

Otherwise you could always do this:









It's another container, but DIY plant geeks already have a PHD in glueing tubes to the caps of bottles. :biggrin:
I should point out that the bottle needs to be able to withstand negative pressure, thick plastic or glass - preferably clear or translucent.


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## scolley (Apr 4, 2004)

Josh - I know the extra jar on top complicates things, and makes it harder to make a physically stable and sturdy unit, but IMO that is an ingenious solution. You could be onto a highly accurate, consistent flowing, inexpensive auto dosing setup.

And while turning jars of ferts upside down, setting them into other jars, sounds a bit messy, you wouldn't have to do it often. I've been auto dosing for about a year and a half, and you would be surprised how long a liter or so of macro ferts goes. A liter of micros would need replenishment so infrequently it's ridiculous.

Great work! Looking forward to progress.


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## Naja002 (Oct 12, 2005)

Ok, I read this-*Slowly*-about 3 times Yesterday and still couldn't quite get it....

I think I get it now-_*Finally!*_ If so, this really is Ingenious!

So let me be sure I'm understanding this:



> What happens is that when the pump is off the fluid level inside the tubing equalizes with that inside the jar. When the pump turns on, the fluid is pushed up the tubing and into the tank by the pressurized air (it burbles like an espresso machine). The pressure in the tubing also bubbles out the inlet hole and prevents more fluid from entering the tube. Once the fluid has been pumped into the tank, air flows through the tubing until the pump turns off.


Basically, the perforation in the Tee is to allow the tubing to "Refill" after an injection, and also creates outward air pressure--keeping any more fluid from entering the tubing until after the injection cycle is complete. And the perforation in the Top is to prevent air-pressure build up inside the container which might force fluid into the tubing during injection. Is that Correct?

That's Really Cool......

This could be built out of 3"-4" PVC and the "Bottle" on top also-Capped with a screw on drain plug for access.


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## josh_simonson (Mar 2, 2006)

*Yup*

>And the perforation in the Top is to prevent air-pressure build up inside the container which might force fluid into the tubing during injection. 

The hole on the lid also allows air in to replace the liquid that's pumped out. Without it the tube won't refil for the next injection. We want some pressure to build so the liquid can rise up the tubing, but we also want the pressure in the tube to be greater than that in the jar. 

The only challenging part of building this thing was getting enough flow resistance in the two perforations that the pump could generate the pressure to push the fluid to the tank. My 2.5ml fills up 20" of mini tubing, so I need to supply more than the pressure of 20" of water to make it go up into the tank.

The worst failure mode for this thing would be if the hose comes off the T. That'd pump air straight into the jar, which would push all of the fluid up the tube and into the tank. Mounting it in the cabinet means that you'd have to generate enough pressure to go from jar level to tank level, about 4' in my case. My pump can't produce that pressure even with no air outlet in the jar, so there's no way it can dump the whole jar of ferts into the tank. If the jar were mounted near tank-water level this would be possible (though unlikely the tubing would come off), and if it were above tank level the jar could potentially syphon out if somehow the pump only turned on for a couple seconds and primed the output tube to syphon.

The other likely failure modes involve plugging of one or both of the holes, which stops dosing, or of course failure of the timer or pump, which also stops dosing. You'd notice a deficiency and be able to fix it before it was serious.


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## esarkipato (Jul 19, 2005)

Welcome, Josh! Agreed with Steve, this is a great little invention. 

I'm not sure the second "holding tank" is really all that necessary . . . . the ratio of volume lost due to lower levels is quite small, especially if you have lots of coils in the bottom! you could have as many coils as you wanted, just make a less potent solution. . . .

Also, it seems that an airline gang valve may be really useful to adjust he amount of pressure when dosing: http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/9904/cid/2348

I really hope to see this idea catch on, I just love the concept of using the air pump rather than a powerhead or submersable!

PS do you have a picture of the prototype?


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## josh_simonson (Mar 2, 2006)

*Yup*

I figure just about every planted tank owner has airpumps that they've retired when they went to CO2.

My prototype doesn't have the second tank to stabilize the fluid level, and I'm not sure I'll bother to put it in considering it's already installed on the tank. I do have some 1mm diameter teflon tubing (for insulating wire) I'll try that first on prototype #2. It may choke off the airflow too much to be able to push the fluid up the tube - most of it goes in one whoosh, but the last quarter ml or so is left as dropplets in the tube that air can get around. If you care enough about precision to want the 1mm tubing, you'd probably want to be sure those droplets are blown out.


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## jgc (Jul 6, 2005)

Great idea. Not sure, but the preferated part probably also agitates - excelent.

Love the KISS principal. Only improvement I can think is a modification to allow for substantially larger dosing.


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## esarkipato (Jul 19, 2005)

I've been thinking about this, and another advantage to the upper resevoir is re-filling: you wouldn't have to unscrew the near-airtight lower container.


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## josh_simonson (Mar 2, 2006)

esarkipato said:


> I've been thinking about this, and another advantage to the upper resevoir is re-filling: you wouldn't have to unscrew the near-airtight lower container.


If you put airline valves between the upper and lower containers, and a valve at the top of the upper container, you could add more liquid by closing the lower valves, opening the top valve and filling, then closing the top valve and opening the bottom valves again.


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## josh_simonson (Mar 2, 2006)

Status update: my original device has been working fine for over a year now in my planted tank. I've refilled the nutes twice when it got to be about half empty. I've been taking effortless growth for granted now, occasional pruning, CO2/nute refills or bulb replacement is all they need to keep things churning along. 

Considering the device cost a jar and $3 of tubing, I couldn't be happier with it.


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## Wasserpest (Jun 12, 2003)

So the trick here is to find a hole/slit/perforation size that is small enough to resist a little bit of air pressure, but large enough to allow liquid passing through without plugging up over time.

What would happen if instead of the perforation in the cover the container would just be left open?


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## dennis (Feb 9, 2004)

So I finally understand this. Like Naja I had to read it about 6 times but I finally tried it and, brilliant! I just tried a little demo with a water bottle and a 20" coil of regular airline tubing in the bottom. I think the coil tends to trap air in itself due the the fact that it is coiled. I am going to try a small container of the correct volume. A quick calculation shows that 1/2" PVC pipe is ~11.85ml per inch. I'll report back if it works.

Wow!


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## dennis (Feb 9, 2004)

Actually, I made a mistake on the math. There are ~4.47ml in 1" of 1/2" PVC.


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## dennis (Feb 9, 2004)

Update... Two things actually. First, I am having a little trouble getting this to work correctly. I have tried both the tube coil and the PVC volume regulator method I mentioned above. Both setups give me a good initial first dose but then I get an intermittent spray or a drop or two every 5-10 seconds. This adds about 5ml or so extra per minute that the pump runs. I have tried several things but none seem to fix, or even change, the problem. I started with a sewing needle hole in the lid and in a 90degree tubing elbow. I slowly expanded the hole in the lid to the size of a paperclip (heated). The bottle I am using is a very thick, 2000ml lab-type Nalgene bottle and the pump is an old, el cheapo "Profile" that was part of a 10 gallon set I pick up long ago.

Also, this happens with the lid on or off and regardless of breather hole size. Both the tubing coil and the PVC chamber do exactly the same thing. It would seem that a venturi forms and a little fluid is continually sucked in to the dosing tube or chamber. 

I suppose it would be fine to simple measure the amount dosed for the entire period that the pump runs or get a time that works in minutes. Having one that works in minutes though is a bit counter productive to a cheap setup since a timer is about $30, half the price of an APT peristaltic pump.

Any thoughts on how I can fix this issue?


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## Wasserpest (Jun 12, 2003)

I played around with this design too and changed it somewhat and still couldn't get it figured out reliably.

Initially, I added a very small slit to the tubing. Very small is somewhat subjective, and in the beginning it was so small that the solution didn't enter the tubing, and later, when it did, air would bubble out of it, turning the flourish into a foamy mess (I want to dose concentrated stuff).

So, I thought, let's play... with some checkvalves. They should work great, allowing the solution to slowly fill the tubing one way, and when the air comes on, block it so all of it will go through the outflow.

Something unexpected happened, which you saw as well... every 5 seconds or so, a little drop of solution made it through the check valve and added to the dosing volume. That wasn't the problem... the problem was that when the air turned off, some drops would still be stuck in the tubing, now preventing the refill action. I had planned on using that sitting in the stand, going up to the tank a couple of feet. If you have it sitting at tank level, with shorter tubing, it might work better.

To prevent the droplets going through the checkvalve during operation, I tried a couple of things. I reduced the outflow at the end of the tubing, which didn't work well - too small, and the tubing would not refill, too large, droplets would still make their way through the checkvalve.

I added a third checkvalve to increase the backpressure so no liquid would make it through the other valve while the pump was operating. Didn't work well either. Maybe adding the checkvalves complicated things too much, and I need to work on the slit thing. Didn't quite understand the need for it to be covered up and "almost" airtight.

Around that time I received some peristaltic pumps, connected them and put the airpump away for later.


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## dennis (Feb 9, 2004)

My issue is that all the timers I have laying around work on 30 minute intervals. The only way for this to be really cheap is to be able to use cheap timers. If I have to go out and buy minute interval timers your talking about $30 each either after shipping or after tax. So,two timers is the price of one peristaltic pump and it can be sized to work for a 1/2 hour period.

I found that having the lid on added some pressure and actually made things work better, though not perfect. I am going to play around with some of these ideas a bit more. We will be off on our wedding/honeymoon in two weeks, for two weeks, and I really need to have something figured out before hand. I don't really have the liberty to spend the money on two peristaltic pumps or two really good timers but the last time I had someone feed the fish and dose the tank, it did not go so well.

I've tried your syringe/timer doser but my timers are only strong enough for a 10cc syringe (which means about 6ml can be dosed) Not enough for me, especially for micros. Larger diameter syringes are to stiff for the timers I have. If, though, I could find a nice heavy duty timer capable of moving a larger syringe, I could add larger wheel and build it to run two syringes at the same time, solving all of my problems.

I certainly need to think on this more....

Thanks for your reply. Your posts have been very helpful and insightful for me.


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## Wasserpest (Jun 12, 2003)

Look for deals on digital timers, Target and WM have them for less than $10, sometimes quite a bit less. I picked up a few that were discontinued models in WM for less than $5, once in a while RiteAid (of all places) has some for free or almost free after rebate.

10cc not enough for you? Wow. My 100gal is (under?)dosed with 4cc daily.

Congrats and have fun on your honeymoon! roud:


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## dennis (Feb 9, 2004)

I dose Flourish and Fe gluconate at 1ml per gallon per week. Yup, its a lot but the growth is good and I have no fish or inverts issues. So, since it has to happen daily, 60ml total for 7 days is 8.6ml daily for micros. Macros I could mix to get the dose right but I was hoping for a fool proof, easy to use and accurate- oh and really cheap- method of autodosing.

My current test setup in the laundry room seems to give about 47ml per 1/2hour cycle. This may change a little if it is moved to the tank if hose length or head heights change. This also uses 18" of airline tubing in the bottom of my container for the initial dose, which is about 7ml if the tubing is full. I've tried all manner of hole sizes and check valve configurations, all yield similar situations, an eventual venturi that spits. I may try modifying the timer I have so that the actuator is narrower, thereby letting the power be on for a shorter period of time. I am sure I could get it down to only 5-10 minutes of run time this way.

The next option is something like magicmagnani's air doser but I don't like the variation in dose size over time, nor have I been able to control it to dose less than several hundred ml in 1 minute.

Bahhh!

Thanks for the tip on cheap timers. I remember seeing some digital ones at Walmart but did not look closely at the time. Now I just need an excuse to go back there.


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## Wasserpest (Jun 12, 2003)

You could also go with Wasserpests water pump dosing  which doses consistently, and you can play with the concentration of the solution to dose the right ppm's. All you need is a little water pump, they can be had for $10-15, or maybe you have a spare one sitting in your stand anyway.

Let us know if you figure out a way to get this cheap liquidoser to work... it has a lot of potential. One of these days I will start poking holes into airtubing again. :icon_mrgr


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## dennis (Feb 9, 2004)

I think this would work perfectly fine if a minute timer can be found cheaply. Because large coils of tubing do not seem to work well it seems adequate to dose only in the 5-10ml range for short periods. I may be able to adjust that by playing around with large "chambers" in the solution bottle. Also, a cheap timer capable of minute intervals would make magicmagani's doser a good solution for toping off a little also. I'll hit Walmart or Target tomorrow and see if there is anything under $10. I would need two doser setups so it seems that going the "cheap" route is only worth it to me if I can do the whole thing for under $30 bucks and with some degree of reliability. Otherwise, if I cannot find suitable timers and need the $25 intermatics, I might as well spend a little more and get the accuracy of peristaltic pumps that will dose the right amount in 30 minutes and use cheapy timers.

Thanks for the help so far.


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## dennis (Feb 9, 2004)

Walmart has Brinks brand digital timers for $8.73. They only have one on-off setting but they work in minute intervals so its perfect. The price is right also. I've done a lot of playing with the concept for the original topic to this thread, as well as magic's AirDoser and Wasserpest's powerhead method.

I'll start a new thread of my own for further updates.


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## JulieJeffers (Apr 7, 2006)

Looks like great idea.

All in all after the time spent shopping and fabricating, why not just get one of these?
http://www.marinedepot.com/aquarium_dosing_pumps_top_off_eheim_liquidoser.asp?CartId=
I’m not being critical; I want to set up something like this and am looking at the pros and cons of each option.

thnx


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## dennis (Feb 9, 2004)

The one negative I saw with the Eheim liquid doser is the amounts it can handle. You can do a max of 1ml, 8 times a day (providing I am reading the literature right). In my case, that is not enough to handle my trace supplementation. You should be able to mix all your macros at a concentration that would work with but it would not be enough for me for traces.


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## Wasserpest (Jun 12, 2003)

> The one negative I saw with the Eheim liquid doser is the amounts it can handle.


I could see a few more negatives... first and foremost, the cost. While one of them doesn't hurt too much, in my case I would need quite a number to supply traces (and maybe PO4) to all tanks. With some easy shopping, I can get a dual output airpump for around $10.

Keep in mind this is a hobby... time spent tinkering with things is something that I don't consider lost, and don't want to do without. Of course, if you apply your hourly wage to the time playing with tubing, you might be better off just to order the Liquidoser.

Another dealbreaker (for me) is that it has to sit on the tank rim, unless you have a sump. I like to cover my tanks as completely as possible, and use a slim canopy that just so fits some T5 bulbs with reflectors. Don't wanna have anything stick out. :smile:


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## tyler79durdan (Jan 23, 2010)

It works great! Here are my photos...

























All it took was a little patience, 2 liters of spilled cool-aid, a broken t, and 65" of my tubing... Iv got a digi timer so Im gonna try it roud:


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## sparkysko (Jun 11, 2004)

I built one too. I didn't understand the issues by just reading..

I haven't been able to avoid a venturi effect on the 'fill hole' at the bottom of the coil. This becomes a problem when you're using a timer that has a minimum of a 1 - 15 minute cycle. Unfortunately I think the venturi is more 'random' that reproducible, and I'm not sure if it can be calibrated with the venturi issue.. I tried adding valves/etc on the fill hole to adjust the venturi, and to keep it away from the coil, but it didn't help..

Instead, I dug out a bunch of the $1 automatic plant watering machines "Green Genius" that I bought at big lots on clearance. They're battery powered, but they have a dial to specify frequency of dosing (i'm using 2 days) and quantity in ml...

Prior to that I did some testing on water pumps, and dug out and calibrated a bunch of 4$ Cascade filters they had on clearance at Petsmart. Used epoxy putty to attach 1/8" hose to the outlet. Consistently within about 5% accuracy over the course of a minute..


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## tyler79durdan (Jan 23, 2010)

I really dont know WHAT YOU JUST SAID... :biggrin:

But it worked with a very small hole in the T. I noticed that this hole was the most important, as it really effected how fast it doses and how fast or slow it fills. Still working on the tubing refill cause it filler 15ml twice in an hour, then it filled 7.5ml once, then 12ish the third time. As long as it at least doses 11 average over a week of tri-weekly dosing, hmm I dont care as long as it doses something. Welcome to my world!

IF ITS GONNA GROW, ITS GONNA GROW! IDK anymore 


But Id guss this really doesnt matter since im changing water weekly!


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## sparkysko (Jun 11, 2004)

I'm saying that it works fine while testing by blowing through the tube, but when you hook it up to an airpump for a minute then additional unwanted liquid enters the coil from the fill hole making it difficult to get an accurate dose.


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## tyler79durdan (Jan 23, 2010)

hmm, still cheacking doses... still averaging 10 ml on a supposed 15ml dose. Its going down!


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## Travis32 (Jan 6, 2011)

Hello, I am looking for a good 2 part dosing system that's cheap and I don't mind if it's a relatively simple DIY project. I found this using Google. Does anyone know if they have gotten this fairly well ironed out or is there still significant issues with this design?

I'm having to dose a fairly significant amount of calcium. Approximately 2 - 3 cups per day of calcium chloride to keep it at 400. Alk remains stable with around 2 to 3 tablespoons of baking soda per day. If I ever go out of town I'll need to auto dose alk also in a dissolved solution. That's in addition to 1.5 gallons per day of top off kalkwater!

In a 125g tank with 30 gallon sump.

I read most of the posts and some say it works, some say it doesn't. I'm not looking for overly accurate, just something that would keep up with my alk and ca depletion on a weekly basis.


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## Wasserpest (Jun 12, 2003)

My guess is that only the OP has gotten it to work reliably.

I'd suggest you look into peristaltic pumps. The "water pump dosing" might work as well, a bit cheaper, with the added benefit of agitation of the solution.

Check out my signature link for various autodosing methods.


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