Step 7: Operation

When air pump is on, the nutrient will be forced up into the planters until the pump is turned off. The nutrient will then return to the reservoir through the help of gravity at a rate determined by the back flow of air through the pump and any leaks. Note: Air leaks are not necessarily bad, but will limit max height the water can be pumped while allowing for faster draining. Small amounts debris are easily flushed harmlessly to the bottom of the reservoir during the drainage cycle.

My timer is set to 2 minutes, but I let it run longer in the video to show what happens when the reservoir empties.

No check valve is required as it can't siphon through the air pump AS LONG AS the reservoir is not overfilled.

There is no overflow protection for the planters so a maximum level of nutrient will need to be established once filled with growing medium. This can easily be marked on the reservoir with the elastic band. Min/max levels should both be established this way. Cannot be seen well in video, but there's a max limit.

Put reservoir and planters in inverted chip bags to prevent algae growth. Double up if necessary. It works great. See DWC unit in finished system photo, but that's another story.

Due to the simple operation and modularity (if that's a word) of this system, it can easily be modified or expanded upon with ease to suit your space or container needs. PSI and volume are your main restrictions.

I apologize for the poor lighting in the video, but I have removed the bag so you can see the progress. Prepare to be bored! Especially by the last minute, forgot to edit that out, sorry.

What a cool idea! Have you (or anyone else) been doing this for long? What type of aquarium pump do you use? How long has it lasted? I'm worried about the pump diaphragm rupturing. How high can you lift water with this? Thanks!
I've had a system, very similar to this one, operating for about four years now, with the same plants you'll see in these instructables. The plants are doing very well (bamboo and Devil's vine) even with major stressing/negligence on my part. <br> <br>It uses a Hagen 802 double pump, without any failures. <br> <br>I'm not sure how high it can pump, but the video kinda says it. <br> <br>http://www.youtube.com/watch?v=aNhpBJmXb9U&amp;list=UUshoxd36btC2QldzMTI3Nrg&amp;index=7&amp;feature=plpp_video <br> <br>You're welcome.
Can you spare some details about your timer setup? I've found some round one on/one off timers, and am not sure what to look for for a setup that goes on and off three or more times daily. Thanks!
I think this system HAS to be a little loose. Just set one up, and the water I used to test it just plain will not drain back into the reservoir! This picture shows anti-siphon valves, because I had them laying around, but even without them the water will not drain! Any ideas on how to make sure the air pressure can be released when the pump is not on? I haven't check for valves that perform this function, but if anyone has ideas let me know! Great work wiley!
As mentioned previously, there is a good chance that your air pump has an anti-siphon built in it (this is because people will still put their pump below the water level - even though the instructions say to never do this without a check valve - so that if the power goes out as siphon wont be created). A lot more of the higher quality ones are doing this now.
Dont know if this problem has been solved yet, but sometimes aquarium air pumps have built in anti-siphons. You can tell by blowing into the hose while it is connected to the pump, If you cant, then it probably does. alternative-innovation.com
Please see <a rel="nofollow" href="http://www.instructables.com/id/Modular_Hydroponics_SkeetaGator/#step4">Air Control Cap</a>. The adjustable &quot;screw valve&quot; can be implemented where convenient.<br/>
What works is if you take the hose off the air pump when you want it to drain. That is what I do.
I don't know how technical you want to be, but a low or middle voltage solenoid valve would allow for this. If the system were tight, an added valve tied into the time would work. Tie it in so it stays energised while the pump is on and it will open and drain when it goes off. A time delay would allow it to keep the fluid to stay up longer if you wanted it to. If you need an electricial drawing, send me an email and I will make one up for you.
Yah, I think that is more work than I am up to. But I did find out there is a hydroponic store in my town, so I might check that out. Good suggestion!
Thanks. Excellent setup. I am humbled. It would slow down the fill rate and limit the height that it could push, but I tried adding a 2 way control valve to create a controlled leak to speed the drain cycle. It worked, but I found it unnecessary as my air pump allows back flow. You could try another pump, but I would introduce an air leak somewhere above the waterline, hopefully a controlled one first. I would leave the anti-siphon valves out altogether because it can't siphon back, especially in your setup, and they would add slight resistance which may be unwanted.
I'm going to try this with my daughter's 4th grade science class, and as we'll be building it in the classroom, I'm not going to have much room for tinkering with it. Nobody has volunteered a pump yet, so if mine doesn't allow air backflow, how large a hole do you think I'd need in the reservoir or air hose? I'm hoping I'll have some spare bottles, but won't have much spare hose handy if I screw it up. Thanks!
Sorry to add more - I'm planning on building with a single reservoir, pretty much straight from the 'ible, so I won't be needing to sync anything. Thanks again for any and all advice.
You may want to consider something like this for a single reservoir system. I know it's not pretty, but it's a work in progress.
Mine is a Hagen Elite802. If you can't find that, make sure that it does not have anti-siphon built in and you should be fine. Try to do all tinkering on the bottles or caps themselves as they are easily replaceable. The tiniest of holes near the top of the bottle should work. The hose is a valuable resource, so try not to mess with it. It really is so easy to build, I would recommend throwing one together, or at least a partial system, in advance and tinkering with it, so your not going in totally blind.
Just an update. I tried putting a very small hole in the cap, the smallest drill bit I could find, to no effect. It seems that even that small of a whole lets out too much pressure. I enlarged the hole and put in a screw, which I can adjust in order to change the amount of pressure in the bottles. Not quite perfect, but as my pump doesn't let air back out, it works for now. Still working on what to plant in these, as no stores have seeds anymore.
Excellent. Whatever works. I've run into similar problems with my pump where the water column was lower and it drains really slow. I've used cheap, 99 cent, plastic 3-way control valves with the variable tap open quite successfully. Here's a pic. I also included a plastic gang valve($4.95) that would work as well. Both left over from old aquariums, but available at any aquarium supply store.
Thanks! Great artists steal. I just cut a little notch on the side of the airline hose hole in the cap. Works fine, but its hard getting the two reservoirs to sync, and I ran out of caps. I'm a high school teacher though, I can get plenty of those. My pump doesn't allow air back through, so the siphon valves aren't hurting anything really. At least I know where they are if i need them. Now I just need to figure out how to start plants going in there!
I was thinking, you could experiment with hole sizes near the top of the 2L reservoir bottles to sync them. The rigidity will give you better control over flow rates and they're easiest to replace if you screw up as well. By varying the hole size in each reservoir, you could approach equilibrium. or for the less patient You could use control valves. If you had a gang of three you could use two to sync the reservoirs and a third as a controlled rate leak or vent. I just filled the bag with pea gravel and old aquarium gravel, threw some mung beans just under the surface and they grew. The cats made short work of them though, once they found them. I didn't think it would be that easy, but that's probably because they were mung beans.
you could also simply add another water pump to pull all the water out instead of pushing it in this way you could extend the length of time the roots are exposed to the water / nutrient solution this would also have to be on a separate corresponding timer
i was wondering if i can use straws interconnected for that and maybe a serial port powered switch by python. especially useful in a server PC hihihi! gotta try as soon as possible!
If you could add something to the bottles that would gradually release pressure, like those nozzles on inflatable innertubes used when sledding, you would definately have something there. or, maybe something which doesn't begin releasing pressure until a minimum pressure is met, and then releases all pressure.
You don't even want to know the overcomplicated, doomed to fail, air powered valve shutters and blockers, pistons and balloons I've contemplated when the answer was in front of me. On a larger system, control valves and the like would be great, but I'm simply experimenting on my window sill and .......... oh yes.........I like the way you think. One of my "motivations", if you will, is to keep it a "hack" job as much as possible. I do like your idea of the inflatables valves. It would actually work the same as the stone if it simply provided enough back pressure to drive the reservoir while providing an escape route for the air during the drain cycle. I've actually added the DWC unit to the air input, essentially an air stone, to release the pressure. It runs normally when the pump is on, increasing the bubbling action as the reservoir empties. When the reservoir empties the pressure is released through the planters and bubbling occurs there. When the pump is off the drain cycle drives the air stone again, slowly releasing the air as gravity pulls the water down. Working on an instructable as we speak regarding same ...................... and more, but have run into some minor construction issues with materials and design. Also wanted to let it run for a week or two first. Should hopefully be done within the next day or two. Note - All stones are not created equal and it's pressure releasing abilities are also directly related to the number of inches the air has to be pushed down through the water to the air stone and therefore the water levels are a MAJOR part of the key. I'm sure there's a technical term for it. It's also freed up my second pump by integrating the two.
I built this system but with three bottles instead of two and it worked PERFECTLY! Very good idea A++++ Wonerful Instructable Thanks!!
Thanks. I'm glad it worked out so well. I've been messing around with some improvements and EVEN cheaper construction methods. Hopefully I'll be able to whip something together soon.
Absolutely wonderful instructable. Going to add some small ribs for stability of the recycled containers and paint them to ward off algae growth but otherwise absolutely great instructable.
Thanks and good luck.
I did this with my daughter's class, as I noted earlier - huge success! I built two setups, and tried to power both reservoirs with 2 air pumps pushing through a 3-way gang valve. Couldn't get enough pressure to do both, but because it's so modular, we were able to fall back to just one reservoir/2 pots and it worked great! Fantastic Instructable! Thanks for the inspiration!
Excellent, thank you, and your welcome. I am further inspired by your success. I am glad you were able to work around the issues in front of them. Stimulates their minds and you get to be a hero. Hope they applauded. PS - I've found the "mosquito" type setup, done as low profile as possible, GREATLY increases the efficiency on the flood cycle. I think the problem arises from the vertical reservoir and that the difference in the column height is so greatly affected by the drop in the reservoir....the necessary increases in volume and pressure cannot be supplied by the little pump, especially if there are leaks/vents. The drain cycle is also MUCH slower, though. I'm hoping to have something, as passive as possible, worked out by next March. Hope that all made sense.
Calling carbonated beverages "pop" FTW.
I was wondering how long it would take for someone to mention that...with the response from the milk bags and all. I like to think it's the most efficient way to spell it. Considering my typing skills, it could have taken hours longer to type "soda", never mind "carbonated beverages".
I believe a high-five is in order.
cool! is there a way to grow avacados with these?
Thanks. I would imagine that a similar setup could be modified to grow anything that could be grown in a planter, or a tidal pool for that matter.
do you think if I put fish in the reservoir they could take the pressure from the pump going on and off changing the pressure? really cool!! :)
I've actually thought about that because I've got a big glass jug that would be perfect. I imagine there's something that could take it, depending on the set up. Is there any similar situations in nature? Hmmmm...... You're right, it would be cool. Too much work, and possible carnage, for me though.
I good Idea for expanding this is incorporting a fish tank into the setup <br/><br/><a rel="nofollow" href="http://www.farmfountain.com/">http://www.farmfountain.com/</a><br/>
That's a heck of an idea! I just happen to have a 55 gal aquarium in my living room right across from our home Hydro unit (slide show to come) Hmmm... ...I wonder what momma (read wife) would say to me hanging a bunch of 1 liter bottles from the wall above the tank?
Thanks. That is beautiful. Till now, I've only had visions of such wonders. I've messed with my fish tank a little, but found the requirements to be contrary to my dislike of algae, electric bills, pump costs and potential labour. I think I'll look back into it, though.
Brilliant! I have used the tube in the cap idea for many things but never this. This set up is referred to as "air over hydraulic" and is a great way to create large hydraulic pressures (lifting your nutes) with comparatively miniscule pneumatic pressures. As we know the aquarium air pumps make almost no pressure. but when applied to the large surface area of the nutes in the pop bottle, creates enough pressure to lift the fluid. Sorry for the preaching but it is the teacher in me loving your idea! I'm definitely going to put something like this together to teach my automotive students about hydraulics! Thanks!!!
Thanks. It would have taken me a couple of pages to explain that not nearly as well. I've been thinking that if I increase the surface area that I will be able to move ever larger amounts of water with the same small pump and will be limited mostly to column height. Works in my head, but then again, I also bought a pair of parachute pants in the 80's and I've been questioning my better judgment ever since.
If you could turn the reservoir bottle on its side somehow, that would provide the extra surface area, but then the placement of the air inlet becomes problematic. Perhaps a 45-degree angle on the reservoir with a short extension of the inlet to ensure it's at the top of the bottle still?
That would work, but volume would be greatly compromised. The 2L bottle is sort of an oddity in the recycle bin with it's rigid, pressure resistive ways. <br/><br/>Another reservoir is needed and the shapes just aren't available for free.<br/><br/>Please see my next one. <a rel="nofollow" href="http://www.instructables.com/id/Even_Simpler_Flood_and_Drain_System_The_Mosquito/">Mosquito</a> <br/><br/>I changed the planter so the reservoir would not be such a limiting factor to volume. I call it the &quot;Mosquito&quot; because it works the same way. Scrap drainage pipe would work great as a giant vein with more than enough volume and surface area below and between each planter to &quot;fill&quot; its needs.<br/><br/>Unfortunately you will lose the &quot;replace-ability&quot; of anything you customize and I'm not sure what effects it will have on the air pump requirements.<br/>
Your are correct, more surface area will = more pressure/lift. I guess the real question is...<br/><br/>... did the pants have bunches of zippers all over them?<br/>
Unfortunately yes. Ooodles to be precise.
How does a transparent milk bag prevent mold? Also, in your image you have the 2L filter/reservoir. Shouldn't this be opaque, so mold/algae cant grow? I like the idea, and I might even add grow lights! Perhaps a split ('Y' hose) with a mesh filter on it to help separate the backwash material that flows back. Or just a filter on the 2L end.
The bag simply allows you to easily remove the plant from the planter, it would not prevent any algae growth that I can see. You could use a smaller chip bag, or equivalent, as a grow bag to keep out light. You are correct about the opaqueness, but then the video would be even MORE boring. It has not been a problem for me yet on this system, but if it was in sunlight, I personally would use an inverted chip bag as shown on the DWC unit. This works very well, I have found. I also want to see if the green plastic would help prevent algae forming in the planters by filtering out some of the other wavelengths...just 'cause. I purposefully left out any filter as they will clog if not cleaned. Any debris that makes it through the tube will be discarded with the waste water. The reservoir simply unscrews for easy replacement. For this reason, in a new system, I would probably use rigid tubing such as 1/2 inch CPVC to better control water flow and prevent dips where sediment can collect over time.
Elegantly simple. So how's the Dracaena enjoying it, and what did you put in your solution? Really nice job, I may give this a try this winter.
Thanks. The small one is dying off completely, but I expected that and the spirally one is still growing. They were in a display that starved the roots of oxygen and the stalks started to rot. It's "died" twice already, so I'm letting nature takes it's course. I used a "complete" nutrient sol'n from a hydroponics store at one half the recommended concentration just to be gentle. I've noticed that there's some really slow release, guaranteed not to leach or burn, granulated products out there these days, with micro nutrients, and was going to give that a try as a supplement in the gravel itself. Just can't leave well enough alone you know. The goal would be to change only water and feed soil bound plants with the waste. I'd really like to see what you come up with. You should see the crap in my head now, it's even simpler...sort of, but I've got to stop somewhere. If only the plants could grow REALLY fast.
Thanks for the reply. I have 3 canes that have been existing in water and gravel for about 4 years and I'm looking for some way to give 'em a "jolt" and see if they'll grow some.

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