Whatchamacallit Flow Technique, But Seriously Folks...

 Deep Water Flow. Deep Flow Technique. What do you call it? Who will decide what to call it? Not I. Although I like it for reasons I will go into here, I’ll just call it Whatchamacallit Flow Technique, WFT. I may seem silly to devote so many words to something so simple, but WFT is occupying a special place among hydroponic methods. It deserves an “official” name and some recognition.

WFT systems can look enough like NFT systems to thoroughly confuse new growers. There are two sources of confusion. On is the PVC pipe-based systems being hawked everywhere by Chinese sellers, many of who care calling them NFT systems.

Well, we can stop that part of the foolishness right there. They are not NFT systems and cannot possibly be used as NFT systems. NFT has very particular specifications, mainly relatively low flow rate, precise slope, a mere film of flowing nutrient, nearly the entire volume of the NFT channel containing only free air, not too long a channel, and a flat bottom to the channel so that roots can spread and take best advantage of the shallow nutrient.

With care, NFT can almost be done in pipe, but not nearly so well as in rectangular channel. The curve of the pipe forces a deeper nutrient stream and forces the roots into a narrow mat in a deeper stream, taking away air space. Not really optimal. My advice is don't do it. NFT grow no better than any other system. It is really only of interest to large commercial vertical growers who accept the problems in exchange for more vertical space from using real NFT channel which is only 2" high.

NFT provides air to roots in free air above the nutrient stream. Aeration of the nutrient is neither necessary, nor I think, very effective, although it does no harm, and I have been a lavish aerator myself. NFT systems are somewhat finicky but can be tuned to work well, especially on a large scale, which is where they really shine in commercial operations. I never recommend it as a first system method for a new grower.

So back to the Chinese things. Let’s look at one and critique it and then move on to something better.

 Note some of the details. One top pipe is fed. Nutrient must flow through that, into its neighbor, in and out of pipes until it reaches the end of that level, when is drains down to the next level where it goes through the whole thing again, before draining to the last level, passing through those four pipes and finally back to a reservoir.

Flow is not according to slope. It is simply the result of one tube filling up to a bit less than half, when it spills into its drain pipe and so on. At some point, it reaches a steady flow state. The depth of the nutrient stream is the distance between the wall of the 2.5” ID pipe and the 1.2” drain pipe in the center of the pipe. That makes the depth at the center of the stream to be about 0.65”. That is much too deep for NFT. That alone disqualifies it as NFT. That leaves a potential of 1.3” of air space. But if a plant is in a net cup in a hole in the pipe, the root doesn’t begin until perhaps half the depth of the net cup. In a common 2” net cup, that depth is 2”, and only the bottom 1” is root. So we take one inch from the 1.3” potential air space for roots, leaving 0.52” (13mm) of roots in free air. Not much. Not enough to provide properly for any plant. So the only option is to aerate the nutrient.

These are three-foot pipes, and there are twelve of them, making the total length 36 feet. There are 108 plant holes. That’s 108 plants hitting a 36-foot shallow stream of nutrient for food and dissolved air. And slope is important here too. If one end of a pipe is high, the plants nearest the intake end get little nutrient. If low, nutrient may flood from the plant holes nearest the intake before the level reaches the discharge pipe. If someone had given me a pile of pipe and told me to build a hydroponic system, I don’t think I could have done worse than this.

Okay. It’s never going to be NFT, but can it work as anything? Perhaps, but we can do a much better Whatchamacallit design, and we can do it in pipe, if we wish with no compromise. So lets look at WFT.

Could it be that WFT is really just RDWC, recirculating deep water culture? It certainly has most everything in common with RDWC. But though I once considered it clearly just a form of RDWC, I now believe it deserves to be recognized as having enough difference to be in its own class, because I believe that for many growers who want pipe-based vertical arrays, this is the way to go.

For one thing, its construction methods are quite unlike typical RDWC systems. For another, I believe the characteristic continuous, robust flow of nutrient intimately through a portion of the roots makes it different from RDWC in which the circulation is to keep a large volume of nutrient refreshed.

And I think there’s going to be some change from DWC in some of the plant uptake dynamics. For one thing, plant roots can secrete buffers to adjust the local environment to the best pH for uptake of a nutrient they want. With a more narrow moving stream, those buffers may be simply washed away, leaving the root strictly stuck with the reservoir pH. And from a design standpoint, WFT requires more careful consideration of how to increase nutrient depth to take advantage of as much of the pipe interior as possible.

I have no real argument with anyone who considers this just RDWC.

It is at this point that I planned to use diagrams to illustrate different methods. But I was instantly reminded again of how terrible we are diagraming hydroponic systems. Some examples.

This supposed to illustrate NFT. It is absurdly incorrect in more ways than are worth stopping to go into here.

 

 I have seen exactly the same diagram labeled DFT, what I’m facetiously calling WFT. But it can’t be that. There’s no air pump. And why is there a timer? If you depend on nutrient aeration to provide for the roots, you don’t interrupt that aerated nutrient flow. Nor do you interrupt flow in most NFT applications. I wonder if the original wasn’t a poor attempt to diagram ebb and flow. The drain is messed up, but the timer and lack of air pump works.

At this point, I think I’ve had about as much fun as I should with the Whatchamacallit Flow Technique thing, so I’ll start just using DWF for Deep Water Flow which is, I think, the best description. It can be assumed that DFT means the same thing. The Internet community hasn’t settled into what to call it.

Here’s another one that is supposed to represent DWF (DFT as they are calling it). 

 

They remembered the aeration requirement. But then they spoiled it by setting the drain more of less flush with the bottom of the tray. If the pump fails, the tray empties and the roots begin to die. And there is no mechanism for controlling the depth of the nutrient in the tray. That would properly be done with a riser drain and would both define the depth of nutrient and keep nutrient in the tray if the pump failed. You don’t get a lot of time to rescue a DWC with a dead pump, but you get more than you do in a dry tray. And if you followed this diagram, you’d be fighting to have the pump keep up with the drain and, at the same time, not overflow the tray, which will certainly happen if something like a LECA pebble gets loose and lodges in the flush drain or roots clog it

Why the goofy diagrams? I don’t know. Probably because someone used one and others just picked it up without examining it. Pity the poor newbie who depends on the Internet.

We will fix those problem shortly, but first let me point out that these can be done in pipe or in DWC type trays.

Think of this one again:

But imagine that it included reservoir aeration and dispensed with the timer. It’s not hard to imagine the chamber the plants are in as a pipe. It is, in fact, in this drawing, rather like one pipe in the Chinese thing, but with the outlet set higher to increase the nutrient depth.

And DFT is what I would propose to new growers who may no longer want to tackle NFT but do want a pipe system. I have made my own diagram of a DWF system. Hopefully, after criticizing others, I have this one right.

 

I will address issues under individual headings.

1.     Nutrient depth. Nutrient depth is most easily controlled by locating the discharge at the appropriate height. In DWF, there is no reason for the nutrient level to be maintained any lower than the level where the roots start. In small diameter pipes, this doesn’t leave much room for nutrient, but because it is circulating, it need not be very large volume. One may install a dam in the discharge end of the pipe, a circle that fits well into the pipe and is glued in but which has a chord cut across the top so that nutrient over the desired level pours over the dam and is discharged. Or, as in my diagram, simply put the discharge high on the pipe end cap. There is sufficient depth that minor difference in slope don’t matter.

Another way to control depth, while preventing draining dry.

  

2.    Aeration. We will be making no effort to keep an air space for roots, so the reservoir must be mechanically aerated by air stone or by venturi aerator. Therefore, nutrient flow may not be interrupted. If you are unfamiliar with the venturi aerator, it is a water pump with a venturi attached. The venturi develops a suction on a tube that extends into free air and mixes that air with the liquid flow, ejecting it as bubbles. It is virtually silent. This is one of mine in a test. Venturis are available from Amazon. A ½” venturi threads into the ½” NPT female of my pump.

 

 

 3.    Intake. The intake point in the pipe should be at least as high as the desired nutrient level. This can be done in one of two ways. One is to bring the intake tube into the end of a pipe cap at the desired level. The other is to bring it into the bottom of the pipe through a bulkhead connector and into a riser, open at the top at the desired nutrient height. Either method insures that, should the pump fail, the nutrient will not drain back through the pump, leaving substantially dry roots without even the residual dissolved air. Just remember that, if an intake is below the desired nutrient level, some or all of it will flow backwards through a stopped mag pump.

 

4.     Run cycle. Nutrient should circulate continuously around the clock. No timer is needed. Stopping the nutrient immediately begins to damage the plant from lack of air. It is quite possible for many pumps to outrun the drain capacity and overflow the pipe. Therefore, a ball valve has been added to adjust the flow to a safe rate. Other than that, flow is not critical at all. All pipe systems are subject to overflowing when they are clogged by roots. They are not very good candidates for living spaces.

 

5.     Adding pipes. One may add pipes, either on the same level or on multiple levels. But each pipe should have a separate nutrient feed from a manifold with adjustable flows between the pump and the pipes. Having individual feeds does two things. One is that it provides each pipe with a continuous fresh and unused supply of aerated nutrient. In the Chinese thing, the last plant in the last pipe is the 108^th to take nutrient and air and is likely shorted of both. Individual feeds also allow the use of ball valves to regulate flow. When pipes are on different levels, flow rates will vary widely from bottom to top. Our magnetic pumps do not produce appreciable pressure and typically have low head ratings. It should be remembered that a pump with a ten-foot head has only the merest near-zero fraction of potential flow at the head height. To get sufficient flow at the top level, we may have to use a pump that would, if flow were not controlled by valves, flood the bottom level too rapidly for it to drain.

 

6.     Drain. Therefore, because of the individual feeds described in 5 above, pipes will not drain into other pipes but will drain individually into another manifold and into the reservoir, or if you like, through individual drain lines to the reservoir. If any other reason was needed to provide separate drainage to manifold for each pipe, consider that if even one plant’s roots clog the pipe, all the holes upstream of it overflow. Heaven forbid it’s the 108^th plant with the giant roots.

 

With the addition of some parts, a Chinese thing kit can be used to build a reasonable DWF system.

DWF need not be built from pipe. Channel similar to NFT channel can be used, as can vinyl gutter with a top added, vinyl downspout or vinyl fence post. Vinyl fence post is particularly good because of its size and shape, and end caps are readily available. And the flat sides all use of risers through bulkhead connections and risers made for ebb and flow applications.

Wrapping up, the theory of operation is indeed exactly that of RDWC. It combines much of the simplicity and ease of operation as RDWC and the configuration of NFT where that layout is an advantage. But I believe it is useful to develop the habit of using the term Deep Water Flow, or whatever term gains acceptance, to provide the reader or listener with the information that it is a channelized system, rather then one based upon tanks. In the end, it’s just another way to provide for all a plant’s needs, but clear nomenclature makes discussion simpler and less prone to misunderstanding.

Given the number of bogus diagrams floating around, I hereby grant anyone permission to use my diagram for any purpose.