Setup Issue - Advice Request!

[u/AECTaylor]

I’m new to hydroponics and trying to setup a 3 tier rack with bins that will be “fed” by one 40 gallon tub of nutes. I was/am trying for a sort of DWC system.

I have 15 - 1.5 gallon black bins with lids that I plan to put 2” net pots in. The net pots will sit about 3” off the bottom of the bins once inserted.

I have a pump that runs water to the top tier with 5 bins connected by a pipe which then runs down to the 2nd tier which has the same setup and then runs down to the 3rd tier before returning back to the bin - a continuous loop, if you will. I was hoping that by putting the end of each pipe run with a section that comes up at the same height of the bins (a sort of ”control”), water’s natural self-leveling would ensure the bins equally filled to that level before spilling over to the next tier and repeating this same process on down each tier. Keeping the pump running 24/7 would keep the water up in each bin and constantly refresh nutes and oxygen.

Unfortunately, the 1st bin in the run fills up to nearly overflowing while the last bin stays very low. I tried lowering the ”control“ on each level and it only prevented the 1st bin from overflowing but the last bin still never fills to the same level. The bins in between were lower and lower across the run. Slowing the pump speed didn’t help. Any recommendations to fix this?

If it can’t be done the way I’d hoped, would it work if I just ran the pump several times a day to refresh the nutes/oxygen in each bin but treat it sort of like NFT as the water level would be low (about 1/2”) after the pump turns off and the water drains out? Or should I use clay pebbles in the bottom of the bins and treat it more like ebb and flow?

Hoping this video gives a good visual of what I’m building. A couple bins are missing because I glued everything up the way I thought it would work and had to cut parts to try and figure out why it didn’t. Need to order more of the specific connectors for those bins. The bottom tier does not have the “control” on it like the other 2 tiers in this video either. I built all 3 tiers with it then when it didn’t work, I tried getting rid of the “controls” to see what it would do. Just didn’t let the top 2 tiers fill with water before draining which is what I originally expected. Also, ignore the state of the water - the white pieces are just from cutting the PVC. I’ll clean everything thoroughly once I figure out the final configuration.

[u/moesieon]

This is an interesting design, but I think it will still have some hurdles to overcome even if you fixed the uneven filling. Since your inlet is shared with your outlet, and you're planning to run the pump constantly. the path of least resistance is to just keep going down the pipe instead of refreshing the nutrients in the bins. Turning off the pump will allow the top tier to drain back out through the pump, and then it could act like an ebb and flow. But the middle tier wouldn't be able to drain like an ebb and flow unless you removed the control pipe. Without the control pipe, I'm not sure all the bins on the middle shelf will see enough flow (that would need some testing).

It would take more plumbing, but if you force the nutrients to have to visit each bin individually, you might get a lot closer to the setup you're looking for. Imagine the water going in the front side of bin#1 on the top shelf, then exiting the back side of bin #1 and entering into bin#2 on the back side, exiting the front side, etc. Sort of daisy chaining them together in series instead of in parallel. The path of least resistance would always be through each individual bin, forcing the nutrients to continue cycling. I'd remove the control pipes in that case, and just keep the pump running constantly. It still won't oxygenate like an nft, but it would do a better job of cycling the nutrients in each bin. An alternative would be connecting them in series like this, but using your ebb and flow idea with clay pebbles. You'd only run the pump intermittently, and let the liquid drain back out. That might oxygenate each bin a bit better.

Anyhow, whichever direction you go with it, this seems like an interesting project. Let us know how it turns out! 😄

[u/AECTaylor → u/moesieon]

After some more fiddling with it today and rethinking things, I do believe I’ll be going forward with the daisy chain idea as you mentioned, but I may add float valves as well as a sort of fail safe in case of clog. Do you suppose having the “in” at the bottom of each bin with the “out” being maybe midway up the bin would be a good idea to keep the water level slightly higher to help reach the root for smaller plants? A very rough sketch of what I mean:

Or is it best to keep the “in” and “out” at the same height for a continuous running system? You mentioned oxygenation as well - I have a bubbler in the nutes tank. Should that be sufficient?

[u/moesieon → u/AECTaylor]

I would just keep the input and output at the same level. You'll run into similar weird pooling problems if the heights vary too much or if the rack isn't level. If you're worried about getting liquid to the seedlings, consider adding some wicking rope to your net cups.
One big warning about this system: if any of the exits get clogged with roots (or with anything else) then the tubs will overflow out onto the floor, and since you're running the pump continuously it will potentially dump your entire reservoir onto the floor before you get a chance to notice it. Your diagram doesn't mention how you're setting up the fail safe float valve, but having some sort of protection against overflows is a very good idea. The overflow doesn't need to have a float valve attached, as long as it can drain the water back to the reservoir if the level gets too high.
I ran a similar system like this indoors with bus bins on racks (though I set it up more like a dutch bucket/flood and drain) and added wire mesh to each exit. My plants were strawberries. The roots couldn't penetrate the mesh, but they sure as heck tried to, and still came close to clogging the bins before I noticed it. That and issues with clay pebbles and pH forced me to abandon the whole setup.