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 Post subject: Optimal depth for DWC??
PostPosted: Nov 26th, '13, 20:30 
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IF, and that's a big if, I decide to expand and build another DWC bed, how deep should it be? I've ready 12, 18, 24", and none have convinced me why their depth was the "best". Does it depend on plant choice? I plan on growing a variety- leafy as well as flowering...if it matters. Wouldn't do anything till the Spring, so have time. Also, if it better to use an epoxy paint or liner? Cost wise, it seems about the same. Cheaper with a double poly liner, but pretty much a wash if I use a EPDM rubber liner. Of course, I would have to add another FT as well...which means another pump...and possibly air pump...and filter...lol


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PostPosted: Nov 27th, '13, 06:16 
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Hey Chris,

I am looking into the same thing at the moment, here is what i have found thus far.

- DWC systems should optimally be around 40-50cm deep.

- The deeper water, a more stable thermal mass is achieved, i.e slower to heat up/cool down.

- aeration should be no more than 1m apart, for long beds, and two per bed for small beds.
(its about water flow v DO, but i am still learning about that) (smaller beds apparently require more aeration due to a lower flow rate)

- the deeper the beds, the more 'room' for roots to grow down and out rather that down and bending along with the flow, so less root congestion, therefore less clogging.

- Mechanical filtration of the best sort is a must before water reaches the beds.

Hope that helps a little

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PostPosted: Nov 27th, '13, 07:32 
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If you search DWC as topic titles only, there are about 10 threads on this question.

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PostPosted: Nov 27th, '13, 08:14 
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Thanks Porter. What's the "turnover rate" for dwc beds this size? That's going to be a very heavy bed. Lots of bracing needed. A 12' x 4" x 15" would be over 3700 lbs...almost 2 ton of water, plus wood/bed material. About the same amount of water I have in my entire system. FT, sump, GB's & DWC bed.


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PostPosted: Nov 27th, '13, 08:27 
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Thank Charlie!

Chris, as i understand it, the same turn over or more for a traditional media system, turning over the fish tank volume every hour, 1000ltr fish tank = 1000lph turn over. For mine i am going to go above that to include filter(s) volume and pipe volume, just because i think it should include that too.

I won't be using a sump for mine and it will be raised 500mm from the ground.

Are you using a sump? is the trough going to be at ground level?

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PostPosted: Nov 27th, '13, 23:27 
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Read the Chattersons farm thread right from the beginning.

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PostPosted: Nov 28th, '13, 05:35 
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Dasboot, I have read Ryan thread pretty much all the way through. I remember him saying he grew lettuce/greens in DWC as shallow as 4", grew others in beds from 10-18", and that he was going to be building something in the 24-25" depth. Also, I recall him saying something about turnover rate from 1 hour to 12 hours, with nutrient rates not being much different with the varying degrees. I was hoping to get a consensus of an "ideal depth"...if there is one. Thanks.


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PostPosted: Nov 28th, '13, 23:39 
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coachchris wrote:
Dasboot, I have read Ryan thread pretty much all the way through. I remember him saying he grew lettuce/greens in DWC as shallow as 4", grew others in beds from 10-18", and that he was going to be building something in the 24-25" depth. Also, I recall him saying something about turnover rate from 1 hour to 12 hours, with nutrient rates not being much different with the varying degrees. I was hoping to get a consensus of an "ideal depth"...if there is one. Thanks.


Sorry coachchris that wasn’t very helpful,in my situation here in Thailand i would favour the slightly deeper bed so as to give me temperature stabilisation my choice would be 12 inch,also i think the deeper beds would help with the huge root systems thrown out by some of the plants. I run tubes but with at least a third of the tube full of water,the tubes are insulated to help with the high temps in the afternoon reducing the need for shade cloth,my plastic on the tunnel now has a nice green/dirt tinge to it that just keeps the temps in the safe range.As in DWC with the white poly my insulation reflects light back to the plants,which i think helps.

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PostPosted: Nov 28th, '13, 23:56 
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No worries...I did see a pic of Ryan's greenhouse and see his different DWC. Shallow for lettuce, deeper for others. I may go that route, add a deep, keep the 1 shallower I currently have.


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PostPosted: Nov 29th, '13, 00:16 
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coachchris wrote:
No worries...I did see a pic of Ryan's greenhouse and see his different DWC. Shallow for lettuce, deeper for others. I may go that route, add a deep, keep the 1 shallower I currently have.

Running comparisons will show up whats best,i am trailing different plants in the tubes,if your interested i will post the results,things like Chinese Mustard have a huge root system I’m growing it in the beds and the tubes,at the moment the tube grown is better.

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PostPosted: Nov 29th, '13, 16:25 
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Ive seen Ryan grow tomato's in 100mm pipes, Im not sure if it was NFT or flooded pipes.

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PostPosted: Nov 30th, '13, 07:41 
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Dasboot- would love any data on results from your tubes and DWC beds. I haven't been overly impressed with my results in vertical towers...possibly because my nutrient levels are still too low for this method?? Notice growth on top is better then growth on bottom. Sun , light should be about the same...so figuring the nutrients are being "used up" in the top few feet of media and the lower part is less nutrient dense? I like the tube idea...except that it's not nearly as space efficient as the towers.


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