Drip Irrigation Systems
Drip irrigation systems or top drip systems are one of the most popular hydroponic systems for growing marijuana indoors. A water pump pulls a nutrient solution from a reservoir and feeds it in a continuous trickle onto the top of the growing medium. From there it runs down the roots and gravity delivers it back to the reservoir in a continuous loop. While an air pump and air stone can be used to aerate your reservoir, the water dripping back into the reservoir is often adequate to keep it aerated. Contrary to popular myth, it is not the pumping of air through the water that aerates, but the breaking of the surface tension of water. The further the fall and/or bigger the splash, the more oxygen is added.
Some growers run their water pump 24 hours straight and others turn it on and off at regular intervals to give the roots time to dry out somewhat, albeit not completely. How you set it up will depend on the stage of growth of your marijuana plants, the size of the container, the amount of water retained by your media and the rate of water flow. A timer and/or an adjustable pump will allow for optimal control.
The containers may be net pots feeding directly back into the integrated reservoir or may be placed in pots or rock wool on a tray that feeds back to a separate reservoir. There are many variations on this theme and there is not a right or best way. Part of the fun of growing weed, is tweaking your system until it best meets your needs.
The main feed line from the pump is usually ½” black poly tubing with ¼” feeder tubes branching to the individual plants. Black is chosen over clear tubing to block light and prevent algae from growing inside the tubing. A hole-punch is used to puncture the main line and the feeder tubes are inserted and friction is usually good enough to seal the lines. Open-ended tubing can be used to feed the plants, however the media can be worn in one spot, creating a hole and the roots will not receive equal amounts of water and nutrients. For this reason the ¼” tubing is usually connected to drip stakes inserted into the media. Drip stakes, also called emitters, work well with rock-wool and similar substrates as it wicks the water throughout the media. They come in various flow rates.
For larger plants, the preferred method is to use drip rings. Drip rings are usually made of copper 6-10” in diameter with many equally-spaced, downward-facing pin holes. This ensures even distribution of nutrients and water. Unlike the stakes, drip rings are placed on the surface and around the main stalk of your cannabis plants.
The downside of a drip irrigation system is that the emitters can easily clog and may require regular cleaning. The main limitation is that this type of system may become problematic and overly complex when growing large numbers of marijuana plants. It is best suited to a small to medium-sized weed garden.
