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Want to move to RDWC but need help planning the system.

M

MadMike

New member
I'm tired of hand watering coco and deep water culture seems easier to set up and manage than a drip system so that's where I'm heading. :) I've done some light searching here on the forums for guidelines but I didn't find any.

Tent is 32" x 48" x 60" -- I've been growing six plants in it to date but moving to 8 and keeping them shorter will fill the room and allow for more head space for the lights.

I'm growing in a 60" tall tent so head space is an issue since I need to push my LEDs right to the roof for my grows. So I'm thinking short height bins that are close to the ground. That makes for two challenges to dwc as I understand it.

1. A short bin doesn't give a lot of air space for roots above the water line.
2. Draining reservoirs is more difficult since the bins will be sitting close to the floor.

I want to go with a recycling system so I can have the main reservoir outside of the tent - better temps and easier access for nutrient exchanges.

Thinking about it, I see that I need to have the water level in the reservoir and the bins at the same height to prevent siphoning.
This is what the room would look like roughly:

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The bins are shown elevated but I guess I could have them on the floor just as easily. It would help with temps since the floor is concrete which will keep it cooler.

Since I don't have any height to drain the reservoir into another bucket for disposal, I guess I could hook up a separate hose to the pump and pump the waste nutrient water out into a taller bucket.
I'm wondering now what the minimum water level will need to be just for the pump to fully immersed. Hmm, depends on the pump of course.

This set up might only have an inch between the basket bottoms and the water level.
It would be great to pump the water to the first bin and then have that flow the next in a circle and then return to the reservoir rather than an in and out to each bin. (Four bins, two plants each)

So first questions are:

1. Are the basket bottoms too close to the water level? Minimum suggested gap?

2. Will the flow from bin to bin be a problem? If the flow rate is high enough all the bins should equalize quickly I think?

3. What is the minimum number of gallons suggested for this set up to not have wild spikes in pH or EC levels all the time?

4. Would it make more sense to go truly sea of green and push the number of plants to say 16 or more to have smaller baskets in the bins? That might make harvest turn over faster actually...

5. Is there a recommended basket size : plant size ratio to guide how deep the baskets would sit in the bins? This would guide how many plants and how small I would need to finish them - can only fit small baskets, move to sog, bigger baskets stay with 6 to 9 (smaller but still not sog really).

6. Can I run the reservoir pump on a timer to say pump for 15 min every 6 hours to just equalize all the bins? Shorter interval, longer interval?

7. Are there low cost, low profile bins you could recommend?

8. Based on the bins and water volume below, can you recommend a good pump?


I just found these bins which fit the above bill at a price I can afford. At 9.5" tall they would match the height of the pots I am currently using. 3 bins in the room, 1 outside.
https://www.amazon.com/IRIS-Gallon-Store-Stackable-Utility/dp/B075RPFR6Z/ref=sr_1_45?keywords=storage%2Btote%2B-clear%2Blid&qid=1554134010&s=gateway&sr=8-45&th=1
Essentially then, the reservoir would just be an access point to the nutrient solution since all the bins would have the same amount of water in them.


The bins are 10 gallons or so. If the baskets hang 3" down into the bins and there is a 2" gap between them and the water, that would allow for about 3-4 gallons each for a total of 12 - 15 gallons total. Hmm.. That actually sounds like quite a lot / plenty.

I'm sure I'll have other questions but help on these would be a great start! :)
 
Here's my set-up. I have my pump in the main resivior and I run feed lines into each bucket. I have 3/4 inch return lines as well. There's an air stone in each pail. It sounds like your system will work just fine. You might want a water feed in each grow bucket though. Just my opinion. Rdwc is the way to go I've found! Good luck
 

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1. Before roots touch water 2”...after 6”
2. Depends on if you system is level or not.
3. Need more information to say in gallons. Looks like you plan on using 30... which is more than enough for just a few plants.
4. Faster harvests... more plants to deal with with smaller yeilds per plant. Up to you.
5. Basket size should be based on plant size. I never use less than 6” for mine.
6. Pump and water chiller should run 24/7.
7. I use 5 gal buckets, you can use totes from Home Depot too.
8. You are better off oversizibg the pump than undersizing one. So I would go for a 1200 - 1800 GPM pump.
Now the real question is, how do you plan on keeping your water cool enough to avoid root rot?
 
Toker1
Thanks for the input!

2" gap - matches what I see everywhere. I think that can fit.

"More plants to deal with, smaller yields per plant." :) I was thinking of the work required to make clones to populate the room and there is definitely some work there. I haven't done much cloning so there is a learning curve and some new set up required. I guess I'd like to avoid that route if I can and just do a little cloning on the side for learning without risking a bump in the growing cycles.

6" Baskets - what size plant do you grow in that? It's always hard to say how 'big' a plant is with LST and such. A photo from the past perhaps? :) I took a look at your current grow and it's in soil - at least the one I could find quickly. ;) I can see a bigger basket being needed for larger plants. SCROGging them would help give them support though.

1200 gpm pump sounds really strong for moving 30 gallons. Do you mean gph instead? I was thinking that 120 gph pumping would cycle the water completely 3 times an hour assuming 25% loss due to friction. I have no idea what the loss would actually be so I'm just throwing that out there. :) Going with 200 gph would be oversized enough wouldn't it?

I didn't mention but yes, there would be air stones in each bin - if I only have two plants per bin I would have one stone under each. I'll need a decent air pump for all of them.

Keeping the water cool... I haven't given that much thought, but guess I should. Hmm..
Is there a maximum temp that should be tolerated for preventing root rot. Root rot does seem to be the biggest stumbling block based on some posts here by new dwc growers and the one I'm most worried about.
The size of the pump is of course a factor here but ambient temps are usually around mid 60's for the basement floor - not in the tent of course. In the tent it's 69-78 or so. Bigger pump = more heat so sizing is a factor but I agree that I should oversize the pump.
I did see someone post that they put in frozen soda bottles in their reservoir each day to keep it chilled which I thought was simple plan. Of course, if you miss a bottle swap you've got problems so it's not an optimum route.

Any input from rdwc growers about how they chill their water would be fantastic!
 
I’ve alway read to keep water around 65-73 f your water pump will add heat to system no mater what. Some put frozen bottles of water in res to reduce temp. I use a water chiller in mine but more cost up front and grow
 
I set my chiller at 69 and normally stays 70ish in res. Also have read about lowering temps in flower can do something about color I believe but don’t “” me on that
 
I do soil and DWC as well. Soil when I plan on leaving town for a while, so this year I skipped the DWC just because of my availability time. In 6” baskets I grow 3 plus footers.
Yeah I was thinking gph. Must have been smoking. Lol
Can’t say exactly, because a level floor vs an unlevel floor would be a factor in sizing. But if you go bigger, you will have more head to overcome that factor.
Avoid frozen water bottles unless you have the time. Try a water chiller. Temps at 68 F are optimal. You don’t want that water to get above 73F. Using hydroguard will allowed greater temp flux but just because you are avoiding root rot, doesn’t meant the water is holding enough DO to support heavy yields.
 
Sorry had a few drinks before reading this last night but like toker said you want water temp to stay under 70 really. I keep mine about 69-70 at first then after a couple weeks I drop to 66-68. I have a 90-100 gal system and use I believe a 800ish gph pump. I bought a current culture system so figured they would give me the right pump for the system. I’m growing 6 with in it. 30” plant spacing. I have 9’ ceiling so highth is not to much an issue. Trying to get mine about 2’ tall before 12/12 switch
 
I cheat and only grow in the winter months. For most of the grow, I actually need a 50W fish tank heater in my reservoir otherwise it gets down to mid 50's. I feel obligated to comment in this thread because I just learned RDWC is the name of the Frankenstein's Monster I cobbled together for my nutrient system. Thank you everyone.
 
A water feed to each bucket is essential to RDWC in my opinion. In an ideal setup it would act as a waterfall giving additional dissolved oxygen to each bucket. A few comments below have referenced water temperature and oxygen in their posts and as a DWC grower it’s important to understand their relationship. As water temperature increases, it’s ability to hold dissolved oxygen decreases. Lower oxygen capacity not only allows root rot to take hold but it also diminishes the plants capacity to produce. Most DWC growers associate lower water temps with fending off root rot when it is actually the higher DO levels that inhibit root rot. The lower water temperature is just a method to achieve higher DO levels. The easiest way to increase DO levels is to use a water chiller to maintain a constant temp of 68-70F. In RDWC or current culture systems, an oversized air pump with large air stones along with feed lines setup in a waterfall configuration can also supply enough DO in water temps of up to 75F. Routine water temps above 75F are not practical in DWC, period. The water will not hold enough DO to allow the plants to flourish.
 
Here is my RDWC in a box. I don't know all the lingo, but I use the top of a 5 gal pail for a bit of elevation gain over the reservoir. The bucket is just a bucket, and the reservoir is a 14L opaque bin. Bubbles in each, and room for a heater or chiller in the res. There's a drain from the bucket that leads into a cheapo inline 12V pump that drains the bucket in about a minute. Bucket holds about 10L. I can get about 5 days out of it before it will run dry during flower.
 

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Wow. You all have given me great info and things to think about.

I should have guess that water temp was related to dissolved oxygen. It's a relationship I know well from my outside pond. :) A water chiller does seem required.

Toker1 - 6" baskets for 3 footers. Great reference point.
@ George4green - Thanks for the gal system to pump sizing. Current culture systems look pretty sweet. 9' ceiling... Luxury!
@ ReeferMadnezz - I like the seasonal grow. I've mainly grown in the winter since managing heat can be an issue mid summer. I can see it really helping with water temps.

I'm going to think about it a little more but I think I'm priced out if I need a chiller. I don't think I can get the misses to approve a $300 additional cost. :(

However, you all have spared me making a half-hearted attempt and only realizing after I have multiple problems that I didn't set it up right or invest the needed amount to get great results. Really, all of your advice has been invaluable!
 
MadMike I have two six gallon reservoir grow boxes that hold four plants each. I discovered the evils of root rot on my second grow and thereafter invested in 2 Hydrofarm 1/10 HP water chillers. I keep the water temp around 68 as well and haven't had any problems.

ReeferMadnezz That is the smart thing to do: it's so much easier to grow when it's cold outside. I live where it gets hot and humid in the summer, so I try to save Sativa-type grows for the warmer months, cuz they can handle warmer weather than Indicas.
 
Frozen water bottles (large ones) melted so fast in my reservoir that I had to reject that as an option.
 
When we start, we have no idea how much it will end up costing to fine tune the grow room environment so we can grow really good weed rather than crap weed. If you can show the misses concrete numbers of what you will save in one year growing your own, perhaps she'll understand that you can't accomplish what you want without the chiller.

And if no one said it above, make sure that your reservoir is 100% lightproof, because light leaks can also cause root rot.

I always say, This ain't no cheap hobby.
 
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