This article appears in Volume 5 – Issue 4 of SKUNK Magazine.
IN THIS SECTION, the most popular systems (DWC, Drip and Ebb and flow) will covered. Keep in mind that both reservoir and wick system units can be converted into active systems with the addition of a pump, tubing, drip emitters and optional features such as an additional reservoir.
One example is a reservoir system in a 4’ x 4’ horticultural tray that holds 8” tall containers filled with LECA (pebbles). Providing a constant stream of water-nutrient solution will increase the growth rate.
Tiny submersible pumps with tubing attached are placed in the reservoir, one for each container. Each tube sends a small steady stream of water to the top of the container, which trickles through the rocks. The roots receive plenty of oxygenated water and the spaces between the rocks provide lots of oxygen.
The redundancy of both the water stream and reservoir systems acts as a failsafe should one system fail.
DEEP WATER CULTURE (DWC)
DWC systems keep the roots bathed in oxygenated water/nutrient solution. The system consists of a submerged container that holds the plant stem in place above the water level. The roots hang down into the oxygenated water – where they have total access to water – and to the nutrients and oxygen dissolved in the water. This promotes extremely fast growth and high yields.
DWC systems require a grower’s keen sensitivity to the plants. Unlike planting mixes that buffer nutrient imbalances, the DWC environment is instantly affected by changes to the water. The effects of these changes, helpful or harmful, become apparent very quickly. Experienced gardeners “read the plant” to determine its health and needs.
The common denominator of all DWC systems is a container that holds water into which the roots hang. The container holds a hydroponic planting medium such as clay pellets or rockwool cubes over the water. The reservoir water/nutrient solution is aerated using air stone bubblers, circulating water or a waterfall.
DWC systems are manufactured as stand alone containers and as sets attached to a central reservoir. Other models circulate the water utilizing tubes that connect the containers to each other. The plants are held in small containers.
HOW TO BUILD A DWC BUCKET
- 3 to 5-gallon bucket (Most standard buckets are 11.5” wide)
- Hard plastic flowerpot drain tray that fits over the bucket
- 6-8” ribbed container to hold the planting medium
- Air pump
- ¼” tubing
- Air stone
- Fish tank heater
- Using a pair of clippers or a saber saw, cut a hole in the drain tray large enough to let the ribbed pot fit firmly inside. Drill a hole in the tray large enough to allow ¼” air tube to slide through.
- Slide the tubing through the hole in the tray. Attach an air stone to the tubing that is going into the container. Attach a small air pump to the other end of the tubing.
- Place a small fish tank heater set at 70° inside the container.
- Fit the tray onto the container. Place the ribbed pot into the tray and fill with LECA.
- Add water leaving about 4” for air. Plug in bubbler and heater.
EBB AND FLOW SYSTEMS (Flood Systems)
Ebb and flow are the systems most people first think of at the mention of hydroponics. The containers or rockwool cubes are held in a tray. Its depth varies depending on the containers’ height. Water is periodically pumped to the tray. The planting medium holds enough moisture between irrigations to meet the needs of the plant.
Ebb and flow systems are easy to construct and their maintenance fairly carefree. They also promote vigorous growth. Ebb and flow can be used to irrigate rockwool cubes or any of the hydroponic planting mediums.
A simple manual ebb and flow system can be constructed using a tray about 6” deep. Attach a flexible ½”-1” tube to one of the sides at the bottom. This tube will act as the drain.
Fill 8” tall planting containers with one of the recommended hydroponic mediums and place them in the tray. Rockwool can also be used. If you are growing small plants just use 4” cubes. If the plants are to be larger, place a rockwool slab down first and set the cube on top.
To water, hold the tube above the tray so it doesn’t drip. Pour the water from the container into the tray. Then place the tube below the tray so the water drains into the container.
If you are using LECA, the first time fill the tray 4” deep with water and let it stand. If you are using coir, peat moss, a peat blend or vermiculite-perlite, fill it 3” deep; with 4” rockwool flood only to 2”. Add more to maintain the level until the medium is saturated. Drain it into the container using the flexible tube. This is more than the maximum amount of water/nutrient solution that will be needed each time the plants are watered.
Not as much drains back in as was poured out. Some of the water is retained by the medium. The irrigation needs of each garden will differ with planting medium, garden temperature and the size of the plants. If the medium feels moist, the plants do not require irrigation.
Automating this unit is not difficult. The garden is placed above the reservoir. A tube attached to a submersible pump in the reservoir pours water into the tray above. A short cycle timer, and optionally a float valve, controls the pump. The tray’s drain is designed to flush slowly into the reservoir. When the pump turns on, water flows into the tray faster than it drains. The recirculating water dissolves dried salts and freshens the water in the medium. When the pump turns off the water drains back into the container from the tray.
An overflow drain installed at the maximum water level prevents plant flooding and other accidents. If a timer rather than a float valve controls the pump’s off switch, this is a necessity.
REQUIREMENTS FOR AN AUTOMATED EBB AND FLOW SYSTEM
- Tray to hold rockwool or containers
- Rockwool or other planting containers
- Planting medium (for containers), LECA/ Vermiculite-Perlite, or Peat Moss Mix
- Short term timer
- Submersible pump
(optional) Float valve switch
Several ebb and flow gardens can be plumbed to a central reservoir using a pump for each garden. The lost water can automatically be replaced from a reserve reservoir.
Ebb and flow system kits and components are readily available commercially. The ready-made systems are convenient, reliable and have ironed out all the kinks that a home built unit is likely to encounter. Components to make your own system are available at hardware stores and indoor garden centers.
Drip irrigation works by delivering water slowly to the planting medium or soil using an emitter installed at the end of the irrigation tubing. Emitters are manufactured to deliver water at a set rate such as 1 gallon per hour (gph). The system consists of a submersible pump that delivers water from a reservoir to a flexible tube that stretches the length of the garden. Spaghetti tubing is connected to the central tubing using connectors that are punched into the main line and fit into the smaller tubing. An emitter on a spike that attaches it to the container or cube is connected to the other end.
Each container or rockwool block is serviced by its own emitter. Different sized plants can each get the appropriate amount of water by using drippers with different flow rates or several emitters. Drip rings deliver water in a circle pattern around the container rather than in one spot. They are a more efficient way of irrigating and are especially useful with LECA. Almost all hydroponic drip systems recirculate the water, so they include a reservoir that catches the drain water.
Drip emitters are used mostly in rockwool systems but they also work well with coir, vermiculite-perlite, peat moss and LECA.
CONSTRUCTING A DRIP SYSTEM
EQUIPMENT NEEDED FOR DRIP SYSTEM #1
- Table or frame with sturdy top such as ½” plywood
- Corrugated plastic (available in home improvement/building supply stores)
- Trough to catch drain water from corrugated plastic made from a rain gutter
- Rockwool or planting containers
- Bucket for use as a temporary reservoir
- Submersible pump used to supply water to the drip emitters
- Spaghetti tubing from pump to garden area
- Drip emitter
- Connectors from main line
- Punch tool
- Sump pump
- (optional) Pressure regulator
- (optional) Filter
- A drip emitter system is easy to make using a sturdy table or by building a wooden frame such as two saw horses. Frames can also be made using steel shelving or PVC pipe. If you are using a frame, place a piece of ½” thick plywood for use as the top. Arrange a slight slope of 2½% (1” in 40”) so the water can drain easily. Place a piece of corrugated plastic over the tabletop so the water runs along the troughs to drain.
- Install a drainage trough along the side of the table or frame. The trough is made using plastic rain gutter. Place a holding tank at the end of the trough to catch the draining water.
- Place the containers or rockwool on the corrugated plastic.
- Set up the drip system using a temporary reservoir such as a plastic bucket.
- First, attach tubing to the submersible pump. Place the pump into the temporary reservoir and install the tubing across the center of the garden.
- Install the spaghetti tubing. First measure the length of spaghetti line required and cut the piece off the roll. Push the connector into the spaghetti tubing. Push the emitter into the other end of the line. Punch a hole in the main tubing using the tool sold with the drip equipment. Push the connector into the main tube and place the emitter into the rockwool or container. Repeat with each cube or container.
- More sophisticated systems use pressure regulators and filters. These options are highly recommended.
- Automated systems continually measure the water’s pH and nutrients and make adjustments as needed. These systems are designed for greenhouses and commercial gardens rather than the small garden. Hobbyists who are computer savvy might wish to check out some articles on designing your own computer-controlled pH and nutrient delivery.
- To determine how large a reservoir is required, run the system with the emitters draining directly onto the plastic. Measure how much water is emitted in one minute. If possible use 100 times that amount. If for one reason or another that is too large a reservoir, use the biggest reservoir you can. The smaller the reservoir, the more maintenance is required.
- Place a catchment bucket at the end of the table to hold water that pours from the drainage gutter. Place a sump pump in the catchment bucket. Alternatively, devise a drain system that returns the water directly to the reservoir. The water is transferred back to the reservoir.
- Place the pump into the reservoir.
The system is ready to go.
EQUIPMENT NEEDED FOR DRIP SYSTEM #2 (FOR ROCKWOOL)
- Sturdy table or frame with top
- 5 plastic gutters, cut four gutters to 8’, cut one gutter to 4’.
- Silicon glue and/or fasteners
- 4 Caps
- Catchment bucket
- Sump pump
- 33 connectors
- 33 drip emitters
- 32 4” x 4” x 4” rockwool cubes
- Large measuring cup
- This is a design for a system that is on a 4’ x 8’ table. Use a table or frame with a sturdy top. Raise one end of the table about 3” using blocks or supports to facilitate drainage.
- Outline each foot of the table’s 4’ width. Position an 8’ gutter in the middle of each marked foot. Alternatively, use eight 4’ gutters that cut across the table’s width.
- Fasten the gutters to the table using silicon glue. If that isn’t sturdy enough use metal fasteners and then seal the fastening using silicon glue. Close the upper end of the gutters using caps.
- Attach a gutter to the table or frame to catch drainage.
- Place the submersible pump with tube attached into the reservoir and bring the tube up to the garden.
- Place 8 rockwool cubes in each gutter.
- Measure drip line length and cut the lines.
- Attach connectors and emitters to each of the 33 spaghetti drip lines and then connect them to the main line.
- Attach an emitter to each of the cubes.
- The spare emitter is placed in the system to check what’s going on. Place it in a large measuring cup to get an exact reading of how much water is being emitted.
No matter which of these hydroponic systems you choose, the systems are easy to make and easy to maintain. Once you get the hang of it, you will probably want to experiment and use your ideas and experiences to develop your own system.
Be sure to read part 1 of this article by clicking here.