Building an in-ground hydroponic system can be a fun, easy, low-cost and efficient solution for producing crops using this method. So, we’re here to help you build your very own in-ground system! Outdoor hydroponic systems are often much easier to run than indoor systems and they tolerate much more fluctuation in pH, total dissolved solids and electro-conductivity. Outdoor systems are also kinder to your energy bill and are often not constrained by indoor space.
Installing an in-ground reservoir for your outdoor hydroponic system is beneficial in many ways. The reservoir stays cooler, increasing the amount of dissolved oxygen in the solution, and thus what’s available for root intake. Dissolved oxygen drops significantly as temperatures rise over 70°F. The solution stays more temperate when buffered in an in-ground reservoir in either a greenhouse or outdoors because the ground always gravitates toward an ambient temperature of around 57°F. With water that cool, you really need to be a die-hard enthusiast to soak in one of these reservoirs! When he was younger, our son Jared enjoyed initiating new reservoirs. Brrrr!
Included with this article is a photo I took illustrating everything you need to build an advanced, solar-run system (excluding the solar panels). We have built several of these on retaining walls so you can walk up to the wall and pick vegetables at chest height. We have also built some of these systems inside greenhouses.
The base system uses 1.5-in. PVC plumbing pipes and standard fittings. The configuration can be as intricate or simple as you want. The fittings do not need to be glued.
The feed system we use is a standard garden drip system or spaghetti tubes connected to half-inch tubing. The hydroponic pots we use are buckets designed specifically to be fed by drip emitters. Rough plumbing can be found at any hardware store. The drip system, reservoir and buckets can be purchased at your favorite hydroponics store, online or at select hardware stores.
Trellises can be made of hog fence or wire mesh with metal fence posts, all of which can be purchased from the hardware store. Solar panels can be purchased at certain hardware stores, online and possibly at select hydroponic stores.
Tips for building the unit
To figure out the specific items required on your material list, first measure out the run of your pipe for your overall system. Next, you’ll need to figure out your count of connecting components, such as T’s, elbows and caps, for both the system pipe and the drip tubing. The connecting components are relatively cheap, so buy a few extra to avoid multiple trips to the store. If you have an odd angle, you can use special 1.5-in. adapters.
Once the pipe is laid out and the connections determined, drill 0.87-in. holes for the buckets. You will need either a 0.87-in. spade or drill bit for drilling holes in the 1.5-in. PVC main pipe. If you count on a long growing season or large plants, position the holes 16-in. to 24-in. apart. Big plants need space to grow. I’ve grown habanero pepper plants using this system, and they reached 3 ft. in soil! As a side note, one of those peppers actually seared a hole in a rubber glove, and we burned out every last person at a Thai restaurant for which we grow produce! Now that’s hot.
Next, find the lowest point of your system and dig a hole for your plastic, food-grade storage bin (reservoir). Spread sand to level out and set your reservoir. Simultaneously fill the bin with water and support around it with soil. Next, drill or cut out a 1.75-in. hole near the top for the 1-in. return pipe, and add your float valve if you want auto water. The float valve must be plumbed with 0.25-in. Pex tubing. The Pex tubing can be run in another white tube to protect it from the sun. Any time you can use white tubing it helps lower the temperature. Keep in mind too that ultraviolet sunlight will degrade Pex tubing over time if it’s not covered.
For an access port in the reservoir’s lid, determine your size/plug cap requirements and cut with a hole saw or knife. You can always lift the lid rather than cut an access port. If you want a heavy duty reservoir, ask a clerk at your favorite hydro store. If you live in a region when temperatures will drop to freezing during the winter, either drain the reservoir, or drop in a piece of Styrofoam board to keep it from freezing and cracking.
Just like standard hydro systems, in-ground systems can have added features such as solar-powered auto watering, water level sensing, TDS readouts, auto feeding and solar-powered nutrient pumping. They can be as simple or elaborate as you wish. The more automated the system, the less work once the system is set up. I gave up packing water and hoses a long time ago; plants going through a gallon an hour per plant is a lot of water to move. Certain solar water timers on the market right now have a water sensing adjustment and can be purchased as solar or battery powered and the water sensing functions can also be used for drip organic soil production.
In-ground hydroponic systems can also be run in conjunction with organic soil gardens. The solar 12-V, 380-gallon-per-hour bilge pump will need a deep cell battery and solar panel system. If you skip the solar pumping, you can use a small mag-drive pump to run the system with low energy consumption. It’s amazing how small these pumps can be, from 280 to 500 gal. per hour, depending on the size of your system. My small solar 12-V pump ran roughly 40-ft. of hydroponically connected plants along with three tiers of organic gardens—all powered from the sun.
Simple, in-ground hydroponic systems can be an extremely cost-efficient solution for hydroponic growing. With a little elbow grease and a bit of ingenuity, you can create a really wonderful, productive unit that can be easily modified and expanded over the years. Don’t forget to incorporate solar as you experiment and grow. Happy growing!
The authors wish to express their thanks to those who contributed to the work and development of this product: Vee from Grodan for her many contributions to the industry and our research; Maggie from Ancnoble for her incredible solar water sensing timer; Neil for his New Millennium nutrients; EZ FLO for its fertigation systems; and Roberts Manufacturing for its float valves that automate the many systems we have built over the years.