This is page 5 of our eight page series on hydroponic flood and drain systems. Click any of the links below to jump to that page.
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Flood and Drain Systems, continued
Another variation on a theme. This commercial flood and drain system, available from CropKing.com, is designed to grow livestock fodder as efficiently as possible. The multiple trays stacked one above the other help make the most of floor space. Note the tubes on the near side of the trays, along with the runoff drain at the far end. This system is flood and drain in the sense that each container is flooded frequently, then drained relatively quickly. However, in many fodder growing systems, the crop is harvested when only 6-8 days old. That allows each individual plant (usually a grass such as barley) to be nourished from reserves within each seed, rather than via nutrient solution. Also note that the water is disposed of after a few uses rather than continually recycled to/from a reservoir. This system definitely costs more than a homegrown system which could accomplish the same thing. However, for commercial producers, it offers turnkey reliability and extremely high cost effectiveness. Fodder growing systems are gaining in popularity for livestock owners in drought-prone areas where water must be used sparingly.
Estimated Cost
I've included this topic, and the next few, to try to give growers some ways to compare hydroponic systems against each other. While these topics are hard to quantify, I offer up the following observations as "food for thought" while planning out a system and making some fundamental choices about which system is best for any given circumstances.
With that disclaimer in mind, flood and drain systems range from extremely simple to fairly elaborate, and it has a range of costs to match. The very simplest form of flood and drain system is nothing more than two containers: a growing container and a reservoir, connected by a tube. The growing container is irrigated by raising the reservoir higher than the container, and then the container is drained by lowering the reservoir again. In this setup, both the container and the reservoir would need to be fairly small simply because the reservoir needs to be raised and lowered, often by simple human power. Since anything over than 50lbs is difficult to raise and lower repeatedly every single day, and water weighs 8 pounds per gallon, that limits the reservoir to about 5 or 6 gallons. That in turn would dictate how large the container can be. If a small container is suitable for your goals, that setup is just about the least expensive possible in the hydroponics world. If you need more growing space than that, one option would be to have multiple small containers rather than a single large one. The total cost would of course increase, but the cost per container would still be quite low. At some point, generally once we're talking about half a dozen small containers, the economics of scale start to imply that a single large container would be less expensive overall.
Once we get into any form of automated irrigation cycle, and a pump-driven cycle is the simplest form of that, then costs go up. The pump itself needs to be sized for the volume of nutrient solution to be used. For small systems, an inexpensive fountain pump can definitely be used. For budgeting and maintenance purposes, assume you'll need to buy two pumps to get started. That way you have a spare when (not if) the pump breaks down.
Another cost variable is the growing medium to be used. As we've already seen, the crop largely dictates what growing medium is most appropriate. Localized access to any given type of growing medium will play a large part of that cost. As with any other product in the marketplace, some growing media types will be markedly cheaper in some areas than others. So shopping around is important to get the best local prices. Shop the top two or three different growing media candidates and make your choice accordingly. One thing to note is that ebb and flow systems generally use more growing media per plant than other systems, so you may need to choose a less expensive growing medium than what you'd otherwise want. Also keep in mind that some growing media, such as sand, gravel, lava rock and hydroton can be reused indefinitely. Other forms of growing media, such as coir will degrade over time, and rockwool can generally only be used once per crop. So as you budget your project, include a few growing seasons' worth of cost to figure out which growing medium is the best choice.
One last consideration is the choice of container and reservoir materials. In other words, what are these two objects made out of? One very common option is to simply use inexpensive household buckets and/or tubs. While this is certainly an option in the short term, and/or for experimental purposes, be aware that these inexpensive materials tend to break down fairly quickly. A thin-walled plastic bin or bucket, for instance those intended for use in the kitchen cabinet, bathroom or bedroom closet, are too flimsy for repeated heavy use. They are likely to crack well before the growing season is over. Secondly, if this system is to be outside and/or exposed to regular natural sunlight, sunlight will break down most forms of plastic very quickly, often within a single year. So look for materials which are intended for outdoor use and or heavy contents. One very good class of materials are livestock-grade water troughs and buckets. These are expected to receive a lot of abuse in a wide variety of outdoor conditions (both in terms of sunlight exposure and temperature extremes). They're tough enough to provide years of service. Another good class of materials are either heavy-duty plastic or metal trash cans, for all the same reasons.
Bottom line, you need to give some thought to your overall goals for this growing system. If this is to be an experimental system with a limited life span, as you get used to how the system works, then cheaper materials would probably be OK. On the other hand, if this equipment is intended to serve under heavy use in outdoor conditions, get the higher quality grade materials even though they cost more up front. You'll be rewarded by several years of trouble free operation.
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