There are several ways to get water to the plants: from the top by hand watering or using an automatic drip emitter system, from the bottom using a reservoir system or wicks. All of these systems are easily set up and maintained.
THE SIMPLEST
Everybody has watered a plant from the top. Water is poured into the container until the medium is saturated. After saturation, water drains from the container. Sometimes the containers are placed in a tray.
MORE COMPLEX
An automatic system is convenient when the gardener is not around all the time or sometimes forgets to water. The systems are often home-made.
Most grow rooms are in spaces without drainage. Systems in these areas use an enclosed system with either a top or bottom reservoir. Bottom reservoirs store water in a space below the plants, perhaps under the platform. A pump running periodically on a short range timer pushes water from underneath through a series of drip irrigation tubes to the top of each individual container. Excess water drains once the medium is saturated. Drip irrigation set-ups and instructions are available at the local garden supply store. Suitable pumps are sold in garden supply stores as well as tropical fish stores. Short range timers as well as the other supplies are all available at high-tech indoor garden centers.
Drip irrigation systems with a reservoir above the garden use a sump pump to move water from the collection tray at the bottom of the garden to the reservoir. Water remains in the top reservoir until a valve opens allowing it to flow through the drip emitter tubes to the containers. Automatic valves with timed opening and closing cycles are available at garden supply stores or can be put together using a closed solenoid valve and timer. Valves are available at plumbing supply stores.
Gardens situated in a space with water and drain can be constructed using an open system. Water from the tap is supplied to the plants using drip irrigation. Excess water runs out the drain.
BACK TO BASICS
THE RESERVOIR SYSTEM
When plants are watered from the top excess water drains out of the container, and is either captured for re-use or drained away. However, house plant owners often put a tray under their plants to capture the excess water. The container sits in the water and draws the water as the roots use the water held by the medium.
To assure that the roots oxygen requirements are met, especially the roots which grow into the water, gardeners sometimes place a fish tank air pump with aerator attached which constantly moves the water. Oxygen dissolved in the water is used by the roots.
This system works best with the drier mediums, which are impossible to get too saturated. A mixture of 5 parts lava and 1 part vermiculite is ideal, but mediums which are compact and hold a lot of water in the particles are too moist for this system. Adding a high proportion of lava gravel or styrofoam pellets helps to dry the medium out.
With the reservoir method the roots sit partially in water. The water level can be up to 20% of the container depth. An 8 inch high container can sit in 1½ inches of water, a 12 inch container can have a water level of 2½ inches. Containers can sit in individual trays, or for convenience of watering they can be placed in a single large tray. Plastic dish trays, lab trays and plastic kiddie pools all make ideal water trays, or a watertight tray one can be constructed from wood coated with plastic resin.
Water can be added through the tops of the containers or the water can be poured into the tray. Gardeners use several methods to maintain this system. The water level should be maintained at a constant level by adding water as it is used up.
Most American gardening books advise that when roots sit in water they may be damaged. In Europe however, containers incorporating the reservoir system are sold as standard items in plant stores. As long as the roots come in contact with air containing oxygen, their needs are met.
A ball valve similar to the ones used in toilets are sometimes used to automate this system. When the water level falls, the valve opens up filling the tray to the desired height. When several trays are being used, the valve sits in its own container and controls the water level of all the other containers. The containers are connected to the central unit using tubes. A constant level of water is maintained.
THE WICK SYSTEM
The very first hydroponic units I ever used were wick systems. They consisted of two plastic containers which fit into each other. The bottom of the top container had been drilled and 3¼" thick pieces of nylon cord were strung across the bottom and hung down into the lower container from both sides. The top container was filled with vermiculite. The bottom container was used as a reservoir and the nylon cord drew up water into the vermiculite and kept it moist. The unit produced some incredible vegetables and flowers. Wick systems are very easy to construct, work well and are trouble free. Moist mixes are suitable for this unit. The wicks act as a self-regulating moisture supplier. It is often used by novice growers because it is hard to make a mistake using this system.
There are several ways to automate the wick system. Probably the easiest way is by placing the containers on a platform above a water tray and let the wicks dangle into the water. One grower took a kiddie pool and placed a pallet inside. The containers rested on the pallet. A flush valve system as described for the reservoir system easily automates these units.
THE EBB AND FLOW OR FLOOD SYSTEM
The flood system is the method most people picture when hydroponics is mentioned. The containers are periodically flooded and then drained. Construction of a manual unit is easy. Imagine a tray with a flexible drain tube on the bottom. The tube is held up in the "plug" position. Water pours into the tray until the containers are flooded. The reservoir, often a water jug, is placed back into position so that it can catch the drain water. Then the tube is placed back into the "drain" position.
Growers often make small automated units. First they seal the reservoir tightly. Two tubes are attached using a bottle stopper. One is attached to an air pump at the other end and pushes air into the top of the reservoir. The other tube goes into the bottom of the reservoir. When the air is pushed into the reservoir the water rises, flooding the growing area. When the pump is turned off, the water flows back to the reservoir. More sophisticated units have a back-flow valve. Usually gardens are flooded twice a day using a short range timer. Larger systems use a water pump to flood the growing area.
After each flooding additional water is added to the reservoir to replace the liquid absorbed by the containers.
Ebb and flow tables are commercially available. These work like the flood system, but only partially submerge the growing container with 2 or 3 inches of water.
Step By Step
- Gardeners choose the system that they feel is right for themselves. All of the systems work well because they supply the roots everything they need.
The choices are
- Watering from the top and letting it drain out.
- Drip irrigation and letting the water drain out.
- Automated drip irrigation.
- Manual reservoir system.
- Automated reservoir system.
- Aerated water system.
- Wick system.
- Automated wick system.
- Manual flood system.
- Automated flood system.
All of these systems are designed to support fast growth. The choice is based on convenience.