I'm planning an NFT system and could use help.

flogrow(9)August 17, 2012

I'm planning a NFT system for lettuce and herbs using 3 inch PVC pipe and 2 inch net pots with 1.5 inch rockwool cubes & hydroton to cover. What's the optimum size holesaw to use when drilling into the PVC? Since the net pots will be going into a material that is round, I'm guessing something smaller than 2 inches would be ideal, but what size?

Also, instead of having the nutrients drain down the end of the PVC and down an elbow, I'd like to put a cap at the end of the PVC run and have some kind of drain on the bottom of the PVC. I'm looking for something that will accept possibly 1/2 inch or 3/4 inch PVC risers to raise the water level to the bottoms of the net pots when roots aren't yet long enough, then remove the riser when the roots have grown long enough. Whatever this threaded piece is, it would have to make a good seal with rubber washers against the bottom of the PVC so that there aren't any leaks. I'd seen something like this on a youtube video, I just don't know what it's called and can't find the video again. An alternative would be to start the seedlings in a deep water culture method until the roots are long enough for an NFT system, but that doesn't seem to make much sense to me.

BTW, I intend to grow everything outside and I'm open to any criticism or something I may be overlooking.

Thanks.

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rebelhead

it will be difficult to get a watertight seal on the curved surface of the pipe. i put the drain in the cap. if you cut a slit in the side of the cap on top, it can be tightened by a clamp. if the drain is not centered in the cap, the water depth can be easily adjusted by turning the cap. i tend to let cost dictate my decisions. so this is how i did mine. lowes sells a flexible conduit fitting for 2.50. it is the straight connector shown. the curved fitting .70 cents and the pvc connector is .30 cents. i used rubber o rings for a seal. o rings come with the flexible conduit connector, or u can get a pack in the plumbing department for 2.50. any way here are the pics. i have to show them assembled because i didn't have any spares laying around and the system is running.

    Bookmark   August 17, 2012 at 11:37PM
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rebelhead

the other

    Bookmark   August 17, 2012 at 11:45PM
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rebelhead

connector inside the cap

    Bookmark   August 17, 2012 at 11:50PM
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rebelhead

if you leave the caps removable, the system will be easier to clean and when you need to replace the nutrient, simply revove the cap to clear this water from the tubes. notice the slot i cut in the cap to allow tightening with a clamp. lowes has them for 1.50. lol the water in the pics aren't leaks, its been raining all day. good luck

    Bookmark   August 18, 2012 at 12:04AM
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rebelhead

notice how i offset the drain so the water depth can be adjusted by turning the cap to the left or right.

    Bookmark   August 18, 2012 at 12:12AM
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flogrow(9)

rebelhead,
The offset drain is a good idea, I'll probably go that route. Why do you have holes on top and along the sides of your PVC runs? And thanks for the pictures of your setup!

    Bookmark   August 18, 2012 at 6:13PM
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cole_robbie(6)

"Nutrient Film Technique" is the awkward name given by the scientist who "discovered" the technique. A true NFT system only pumps a small amount of nutrient solution into the very end of the channel, which is angled at a specific incline. A very thin film of nutrient solution runs down the channel. For this reason, a true NFT must have a flat bottom. They look like this:
http://www.farmtek.com/farm/supplies/ProductDisplay?catalogId=10052&storeId=10001&langId=-1&division=FarmTek&productId=536001

Probably what you mean by 'NFT' is a machine more closely resembling the GH Aeroflow. It looks like this:

http://www.4seasongreenhouse.com/images/Aeroflow2-30-Aeroponics-system.jpg

The difference is that the spray line sprays down at intervals throughout the entire tube, and the water level is deeper. GH uses a flat tube, and I think that is probably due to the rubber grommet sealing around the adjustable drain pipe better that way.

If you want to use pvc pipe, I would permanently cement a pvc drain pipe at your best guess of where you want the water level. If you are spraying water like the GH Aeroflo does, it does not really matter what level the water is at, because the spray droplets bounce up and wet the underside of the nets pots anyway. Obviously, you have to move enough water and bounce it around in the right places. If you want to raise the water level with the cemented drain, just use a rubber quick-connect and attach it to the drain pipe from within. Cut the top down to the level where you want the water.

The biggest challenge of outdoor hydro is dealing with the hot sun cooking your roots. If you're in Florida, I think your NFT would work ok in the winter, but you might have temperature problems with your roots in the summer. You could try burying the reservoir. I'm going to go with recirculating deep water culture for my greenhouse hydro lettuce, mostly due to fears about heat. It's the same idea, just with a larger mass of water to insulate the roots from the hot outside air.

    Bookmark   August 18, 2012 at 10:20PM
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rebelhead

the holes are only in one tube. its because its sewer pipe and came that way. it used as a lechate pipe in a septic system. i bought it at lowes because it was 6.98 for a 4", 10' stick. however my local hardware store had some without the holes for 7.90 so i bought that for the second.

    Bookmark   August 18, 2012 at 11:52PM
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grizzman

If you run drain pipe through the bottom of trough, regardless of bottom shape, use PVC glue. Apply it thick and let it set up and nothing will leak. I like to run a piece of coupling through (just slightly)and glue in place well. that way you can easily ad various heights of pvc to adjust how deep the water level is.

    Bookmark   August 19, 2012 at 9:05PM
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flogrow(9)

Thank you all for the replies. You are correct about the heat here in Florida that's why I was thinking of a continuous running system within a somewhat insulating pipe, but now I'm wondering if DWC/lettuce raft might be a better (and easier) way of growing leafy greens outside. OTOH, I might be able to grow more of a variety of things using the more sturdy PVC route�

" If you run drain pipe through the bottom of trough, regardless of bottom shape, use PVC glue. Apply it thick and let it set up and nothing will leak. I like to run a piece of coupling through (just slightly)and glue in place well. that way you can easily ad various heights of pvc to adjust how deep the water level is."

Could you post a picture of what that looks like? I'm trying to picture that as it sounds like what I was originally thinking, but I see a lot of people on YouTube using offset drains on the end pieces quite a bit as well. I'm just learning about hydroponics and find it kind of fascinating. Right now I'm using a small Hydrofarm ebb & flow system and am having good results indoors.

    Bookmark   August 21, 2012 at 7:05PM
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grizzman

I don't have anything running like that at the moment. this picture is the same principle but just through a pvc gutter:

Here is a quick sketch to show what I'm talking about:

    Bookmark   August 21, 2012 at 10:52PM
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rebelhead

one more tip i learned the hard way. lol when drilling the holes in plastic with a holesaw, the teeth with grab hold of the plastic. i almost broke my wrist a couple of times. running the drill in reverse will prevent this. the pvc is easy to drill through in reverse.

    Bookmark   August 22, 2012 at 12:54AM
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grizzman

That's one heck of a drill you're using rebel. My little cordless drill doesn't have the torque to do that kind of damage. Though I have ruined various lids and tubs when the plastic is more brittle because of said teeth catching.

    Bookmark   August 22, 2012 at 7:30AM
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cole_robbie(6)

It looks like you have a coupling on the pipe where it goes through the drain hole. If you drilled a smaller hole, which the pipe could fit through, but not the coupling, and put the coupling inside the tube, the edge of the coupling would help to hold the drain pipe in place and make it stronger.

    Bookmark   August 22, 2012 at 10:19AM
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grizzman

yes, but then the minimum depth of water is the height of the coupling. In my sketch, you keep the top of the coupling as low was possible so you can, if you desire, keep the level of liquid in the pipe next to nothing. Or you can add different heights of pvc if you do want it to hold some volume.

    Bookmark   August 22, 2012 at 4:09PM
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cole_robbie(6)

oh, ok. I get it now. The bottom joint is glued but not the top joint. You could just swap out unglued pieces of pvc to change the water level.

What brand of PVC glue do you use? I have used JB Weld with success. I think everything sticks better if you wire-brush the surface first.

    Bookmark   August 22, 2012 at 11:08PM
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grizzman

I use the orange stuff for house plumbing. if too much leaks inside, I'll run a small bead of silicon around the inside edge for extra measure.
In low pressure systems, I typically don't glue any of the connections except in special situations (such as here where we're creating a unique detail)

    Bookmark   August 23, 2012 at 7:54AM
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cliver mcguiver

PVC can be tapper and the pipe threaded, I have used the pieces left over from drilling the hole to laminate the pipe for better tapping. It looks like you are using an SDR 28 rural sewage pipe, it is a bit thin for tapping with out the lamination.

    Bookmark   August 23, 2012 at 7:09PM
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grizzman

If I wanted to tap and thread pipe as you're suggesting, what would the product I buy be called and could it be gotten at aLowe's or harbor freight type store? Also, how much would it set me back?

    Bookmark   August 24, 2012 at 9:09AM
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flogrow(9)

I believe you would need something like this which I don't think Lowe's sells. In addition you would need the correct drillbit size for the thread tap.

http://www.amazon.com/Vermont-American-20355-Carbon-Steel/dp/B0002YUXEW/ref=pd_cp_hi_0

http://www.amazon.com/Vermont-American-20374-Carbon-Steel/dp/B000M2WOBE/ref=pd_cp_hi_0

    Bookmark   August 24, 2012 at 12:11PM
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cliver mcguiver

A tap and Die set with the right drill bit to match the tap.
They are not cheap but no oil/lubricant is required as in tapping steel.

    Bookmark   August 24, 2012 at 7:33PM
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cliver mcguiver

A die will produce a NPT thread (national pipe thread) and it can do a running thread as in a bolt but the part that makes the seal is the 2 to 4 threads from where you finish the thread. There you can use a little Teflon tap to gain a seal...

    Bookmark   August 24, 2012 at 7:49PM
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cliver mcguiver

I find that a great way to connect piping is what I call the push fitting. I think I coined the idea. I Can drive down a street where construction is being done and see a water heater box in a dumpster and if a home run system is being used I will find a lot of 1/2" pex pipe in the garbage. Put it together like this.

    Bookmark   August 24, 2012 at 8:08PM
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cliver mcguiver

OPPs. next photo.............. The reamer bevels the inside of the pipe and the Teflon tape on the plastic PEX fitting is pushed in to the pipe.......

    Bookmark   August 24, 2012 at 8:12PM
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cliver mcguiver

My system looks like this...

    Bookmark   August 24, 2012 at 8:14PM
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grizzman

any reason for PEX vs PVC?

    Bookmark   August 25, 2012 at 8:34AM
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cliver mcguiver

For me PEX is free and reusable.PVC needs glue.

    Bookmark   August 25, 2012 at 10:02AM
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grizzman

why is PEX free? because of what you do?
And I almost never glue pvc. it only requires glue in high pressure systems.

    Bookmark   August 26, 2012 at 10:08AM
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sdgrower

I purchased both taps and dies at Ace hardware. The taps are much easier to use than the die but both work on Schedule 40 PVC. For using the die you need to make something to hold the pipe while you thread it, and is difficult to thread straight but it works well for the low pressures pumps produce.
The taps are easier to use. You can get away with using a drill bit slightly smaller than what they recommend with the PVC ad the tap does fine.
The barbed fittings made from HDPE make a good seal with the PVC and don't need Teflon tape, HDPE threaded with and HDPE fitting seals well too. PVC on PVC seals ok most of the time but sticks sometimes and can be difficult to tighten.
If using a spade bit to drill holes put PVC in sun to warm up and wear goggles and go slow or it may crack, I prefer hole saws for anything I tap.

    Bookmark   August 27, 2012 at 1:05AM
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cliver mcguiver

If you used a slight amount of lubricant - dish soap might work - it helps to keep the threads from binding and will seal a little deeper.

Great R & D on the taps and dies sdgrower...

I do not hold the handles when starting a die on - I use the palm of my hand to square it.

    Bookmark   August 27, 2012 at 8:53PM
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cliver mcguiver

Grizzman

I Can drive down a street where construction is being done and see a water heater box in a dumpster and if a home run system is being used I will find a lot of 1/2" pex pipe in the garbage. It is quite cheap. Never buy from a roll of pex - it is a pain to work with. They sell 20 foot lengths about 5 bucks at the wholesaler.

    Bookmark   August 27, 2012 at 9:16PM
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