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Advice needed on nearly complete instructable

Sorry this is a bit long, but there is an actual question at the end, honest!

Every morning at work I walk past a table at the end of our mailboxes that people put give away items on. Its usually a catalog of some form but for a long time now there's been a stack of empty CD spindles and a sign beside them that reads "free to good home." I could have taken them and sorted the mountain of CDs in my office or used them for small parts bins, but to make it areally Good use of empty CD spindles I had to ask myself "IS there an instructable in this?"

There are some good ideas for using CDs and a few for the spindles, but at the moment what interests me is hydroponics. So using CD spindles or more exactly the plastic covers they come with I built the basic part of this excellent instructable:

http://alturl.com/oa2qt   

and I learned a lot of stuff about water pressure and such and once I had built the 2liter bottle method described above I decided to try sealing one of the CD cases and use it for the water container at the bottom of the stack.

That took about 4 sticks of hot glue and a couple of burnt knuckles to get a good seal. Turns out there's holes in the center spindle too but I didn't notice them till I had hot glued the container closed. Also ignore the bit of blue air hose inside the container, I was up way too late and flipped the CD spindle 'right side up' which caused me to attach the air hose to the wrong outlet and basically made it useless.

I thought I'd need a lot more water in the system than I do so I chose to use a 100ct CD spindle instead of the 50 ct spindles you see on top. (Thanks to all for the ideas on how I could have done it easier!) So far this part of the project was just overlaying the ideas in the excellent instructable above onto the materials at hand. So what I ended up with is an air pump from a fish tank pumping air into the bottom chamber. (the clear hose in center of picture.) This builds up enough pressure to push water thru the blue hose and up to the top CD spindle.

I've cut holes the diameter of the air hose into the base of the spindle and this lets water slowly trickle into the Perlite growth medium. When the water reaches the bottom it goes out similar holes in the clear plastic CD cover and starts to pool up a bit to start the process all over again. There is just enough lip on the lid and the bottom of the next spindle to keep it from spilling down the side before this happens. It helps to use the same brand CD spindle all the way up.

The clever part of this instructable is that each CD spindle easily stacks in place and you can remove it or change the order without having to dig up or harm the other plants. The base is very stable with several ounces of water in it and I'd imagine you could put 4 of these in a stack and happily swap plants in and out all summer long. The height of the stack depends on how strong your air pump is. I tested two different ones and both were capable of lifting water over 4 feet  up the air hose.

Caveat: I haven't actually grown any plants in this yet, so your mileage may vary.

Using the stack of CDs for use as apartment planters or sprouting medium would have satisfied the original curiosity for what to do with all those left over CD cases, but in absence of glowing blue LEDs or CO2 lasers I thought Hydroponics would be a great way to sex up the overall idea.

I imagine you could use spanish moss or bedding in place of the Perlite, or even soil if you used a coffee filter to cover the holes till you were ready to stick a seedling thru it.

This Instructable isn't quite finished as presented. There's a small problem. As you can see in the photo there's a half height (25ct) CD spindle between the water container and the stack of planting modules. Remember that hole I mentioned in the end of the CD spindle? I closed that with a bit of plastic and hot glue, but it made me wonder, COULD I put some sort of check valve here to allow unused water to trickle back into the holding tank YET not lose the hard fought air pressure that's pushing the water to the top of the column in the first place?

Since I'm re-using all this old aquarium tech I thought I'd try one of those tiny check valves that keep water from backwashing into the air pump when its off. I'm not sure if it will work in this application or even how much air pressure it will tolerate. This will require some disassembly of the CD hydroponics tower and I thought I'd ask here for suggestions before heating up the glue gun again.

So what do you guys think? This has been a lot of fun to think about and I can't wait to bring the media guy  around into my office to see how I've re-purposed the spindles. Just this one last step away….

cheers,

flashj
 

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