DIY Hydroponic Systems

This section describes a number of systems made from easily available, low-cost components that can be put together in a couple of hours.  Construction of the following systems are described:

• A simple air driven one-pot system for a single plant

• A manually irrigated (watering can!) vegetable trough

• A flood & drain table

Having read this far you should be able to see how these simple systems can be adapted for your own use and changed to incorporate locally available materials. All the systems illustrated here can be made for a fraction of the cost of ready made systems and are every bit as good in terms of both build quality and more importantly, crop yield.

This describes a single container hydroponic system driven by a cheap air pump. A water pump can be used, this having the advantage of being hidden within the container and being a little less noisy, but a little more pipe-work is needed to carry the nutrient mix to the substrate.

The components are:

• A container of the type used to store food is used; 200mm square and 250-300mm deep with a tightly fitting lid is ideal. It should be deep enough to take a 150mm diameter open-structured pot with at least 100mm depth beneath it. This gap will contain the nutrient.

• An open structured pot.

• A cheap air pump.

• A meter of 5mm airline hose.

• An air stone.

• Substrate. Clay pebbles, vermiculite and/or perlite.

The container is available from supermarkets and discount stores. The pump, pot, airline hose and air stone are available from an aquatics store and the substrate from a garden centre.

This system is so simple it hardly needs a detailed breakdown of its construction.

1. A hole is cut in the lid slightly smaller than the diameter of the pot. When inserted into the hole the pot should be supported by its rim.

2. A 5mm hole is drilled near the edge of the lid. One end of the airline hose is connected to the pump; the other is passed through the hole in the container lid and connected to the airstone. The air stone should sit on the bottom of the container, near the middle.

3. A single plant is chosen and its roots washed clean of compost if it was grown conventionally. The substrate should be washed to remove dust if a granular material such as perlite of clay pebbles is chosen. The plant is then bedded in the substrate.

4. The container is filled with nutrient mix to a level just touching the base of the pot when fitted.

When the air pump is turned on bubbles break on the pot, keeping the substrate moist. Additionally, the air keeps the mix from stagnating. The pump can be used with a time switch to regulate its use, continuous operation is not necessary as long as the substrate is kept moist. Periodically the mix is refreshed with new, at about a two week interval. Testing for pH and EC is beneficial, as it will maximise nutrient availability but is not strictly necessary. The nutrient should be changed every two weeks. Water your garden with the old mix.

 A more decorative container can be chosen to fit better with your interior décor, this one was chosen as it makes the components visible for the purpose of explanation and was available at the time.

This describes a very simple system that relies on nutrient being applied by a watering can to provide a means of growing root vegetables. Two trough shaped containers are used, one sat inside the other. The substrate in the upper of the two containers is flooded until it is saturated, excess run-off draining into the lower container. This can be poured back into the watering can for reuse when the substrate has started to dry.

 The components are:

•  Two trough shaped containers the depth of which is determined by the type of vegetables grown. In this instance the system will be used by my daughter as an introduction to hydroponics as a school project in which we’ll grow small round carrots. A depth of about 200mm is sufficient for this and other globe root vegetables such as beetroot.

• Substrate. We chose a mix of perlite and vermiculite. Perlite for its open structure and vermiculite to retain some moisture and provide a good germination media as we’ll be sowing directly into it.

• Porous lining material such as hanging basket liner or sphagnum moss.

 The containers are available from supermarkets and discount stores and the substrate from a garden centre. Look for loose bags of perlite and vermiculite rather than pre-packed named brands. The material will be identical and a fraction of the cost.

The trough is watered as needed with plain water at first, weak nutrient mix after germination and full strength solution two weeks after that.  When harvested, the substrate can be brushed off back into the trough and the area replanted immediately for continuous cropping.

 The system is extremely cost effective as there is nothing mechanical to break or wear out and the planting media is completely reusable. With a little care this system will last for many years.

	Two containers with lids are chosen. Size will depend upon the crop grown. We are growing shallow root vegetables as a first hydroponics school project so these are about 200x200x800mm. If we were growing larger root vegetables or wanted continuous cropping we would have selected larger containers.
	The substrate will be a mix of 2-to-1 perlite and vermiculite. These bags retail at about 1/3rd the price of pre-packed named brands and will be more than enough for this project. The liner shown here is a porous plastic-backed material used to line hanging baskets. Other materials such as moss could be used instead.
	Holes are drilled in one of the containers to provide free drainage of the substrate when it’s flooded with nutrient. This ensures that the substrate doesn’t become waterlogged and provide a good supply of air to the roots.
	A section of the liner is cut and fitted inside the drilled container. This will retain a small reservoir of nutrient giving the substrate a buffer and prevent smaller particles from blocking the drainage holes.
	The perlite and vermiculite is added to the container in roughly 2-to-1 proportions. The perlite provides good drainage and the vermiculite will retain nutrient. The vermiculite contains very small dust particles that may irritate if breathed in so should be damped down before use.
	The two materials are mixed in the trough until thoroughly blended.
	The substrate filled container is sat inside the second. Inserting two small spacer blocks of wood, one at each end, makes a larger space between the two. This will allow more room beneath the top container for nutrient run-off.
	Here the gap between the two containers can be seen. 50mm is adequate as we will stop applying more nutrient the moment we see drips leaving the top containers drainage holes.   The top container is now completely saturated with plain water and the drainage checked. Seeds do not need nutrient at this stage.
	Now we’re ready for sowing. Two narrow drills are sown directly onto the substrate surface and lightly covered. Subsequent watering should be done using a rose attachment to the watering can to avoid washing the seed too deeply into the substrate. If you don’t have a rose than an open structured pot can be used to disperse the flow. If you don’t have either then very carefully water either side of the rows of seed.
	One of the lids is fitted to retain moisture during germination. The lid provides the added advantage in our case of preventing carrot fly from getting to our crop during the early stages when we will thin out the weaker seedlings. It’s during this time that they are attracted by the smell of disturbed seedlings; we can simply replace the lid after thinning.

This describes how to construct your own Flood & Drain Table from low-cost components.

The principle of Flood & Drain is based on having the plant roots periodically bathed in nutrient. The nutrient then drains, leaving the roots exposed to the air. This cycle repeats every hour or so using a small pump attached to a timer.

Most Flood & Drain systems consist of two trays, one for the nutrient sump and the other for the plants to sit on. Open structure plant pots can be used to hold the inert material, such as clay granules, perlite, vermiculite, or coco fiber, into which the plants root. The material holds onto some of the moisture after the flood cycle and gives the plants a level of support. Alternatively the tray can be completely filled with the material and multiple plants bedded into it, care being taken to make sure that the inlet and overflow don't become blocked by bedding material or root growth.

The components are:

• Two large storage containers, one deeper than the other. These should be reasonably strong.

• A small water pump.

• A meter of tubing to fit the outlet of the pump.

• A water butt connecting kit, the sort used to chain multiple water butts together.

• Substrate. Clay pebbles, vermiculite and/or perlite.

• A time switch.

	Two large containers form the basis of this system. These are sold as storage trays and measure 600mm x 900mm. The deeper of the two will be used for the nutrient sump. The shallow tray stacks inside the deeper one and is supported by it at the edges.
	Here the shallow tray has been drilled with 25mm holes to take the connectors that will form the inlet and outlet for the nutrient.
	Off-cuts of plastic drainpipe were placed in the deeper tray to act as supports for the table top which will get heavier when full of plants and nutrient. The extra weight may cause an unsupported tray to bow and ultimately crack.
	Here are the parts of the water butt connector kit. It consists of two screw-fitting connectors and a length of corrugated tube. One of the connectors has a short length of 10mm tube fitted into it, this will be the inlet connector from the pump. The other will have a small up-stand, made from a length of the corrugated tube from the kit. This is cut 25mm shorter than the depth of the shallow tray and forms the overflow outlet, returning nutrient to the sump.
	The connectors simply screw together with a washer between the two parts of each. Here the outlet connector is fitted into one of the holes. A soft washer is fitted and the screw tightened. As the components are plastic care should be taken not to over-tighten, any small leaks or drips will simply return to the nutrient sump below anyway.
	A short section of the corrugated tube is cut to a length 25mm shorter than the depth of the shallow tray. This will act as the overflow pipe when the level of nutrient has reached the maximum depth. This returns nutrient to the sump. Care should be taken when putting the table in its final place to make sure that the overflow is working before nutrient slops over the side of the tray.
	The other connector is fitted into the inlet hole. The extension points down into the sump ready to have the pump outlet connected to it. The other end of the connector fits flush to the inside of the shallow tray. Nutrient will flow back to the sump through this connector when the pump stops and it's important not to have the plant roots sitting in a pool.
	A small pump from a local aquatics retailer will push the nutrient into the upper tray from the sump. This pump uses 10mm tube to connect the pump outlet to the upper tray inlet connector. A hose clip can be used to secure the tube to the section of tube sealed into the outlet connector. A simple wire-wrap or cable-tie can also be used, as the fitting is low-pressure.
	With the tubes connected the upper tray can be fitted into the lower nutrient sump. The pump cable fits conveniently in the space between the two trays.
	Here's the finished Flood & Drain Table. All that's left to do is move it to the greenhouse, fill the sump with nutrient mix and the table-top with clay graduals ready for the plants, taking care to wash dust and small particles off before use. A cover (dustbin liner) will be fitted later to prevent algae and evaporation. A timer will control the flood cycle up to once every hour, running for a 10-minute period before allowing the table to drain. The table should be shielded from sunlight using black plastic or other suitable material to prevent algae from growing in the sump. This has been omitted from the images for clarity.