DFT (Deep flow technique) Almost identical to NFT, except a round PVC pipe is used causing the water to be deeper in the center of the pipe. Under high temperature conditions, this can cause an oxygen deficiency in the roots, but under normal conditions, the system works very well. 7/8th inch holes are drilled cross ways near the top so a piece of 1/2 inch PVC pipe can slide through 3 or 4 pieces locking them together so they do not roll. In the picture, the locking PVC is half way down the pipe. 4 inch thinwall PVC can be used to grow most plants. The roots will not back up the nutrient as long as no more than 1 to 2 quarts per minute is used. For the larger plants 1 1/16 inch holes are drilled and 3/4 inch thinwall PVC sleeves are used.
The advantage of the NFT and DFT systens described above is excellent growing conditions without need for medium, plus simplicity. The main disadvantage is the necessity of growing plants in some type system until they are large enough for the roots to reach the nutrient flow, and the short life of the plants should the pump quit or the nutrient be lost.
The sleeves used in the NFT and DFT systems to hold and stabalize the plants can be made by cutting 1/2 in and 3/4 in thinwall PVC into 1 1/4 inch piecies, then flare one end by compressing in a vice with a piece of metal that is round, tapered like a cone and larger on one end than the PVC tube, until one end expands outward as pictured. These sleeves will fit good into the 7/8th and 1 1/16th inch holes in the downspouts and 4 inch PVC pipe.
A drum set up and ready to start. Pieces of screen are held in place with 2 old 1 gallon pots. This keeps debris out of the tank and prevents mosquitos from breeding in the nutrient. The center hole is used to add water and nutrients and check nutrient levels is also covered with a small pot. The tank will be painted white to help keep nutrient temperatures down. If this were a cold climate, I would paint it black to try to raise nutrient temperatures.
The above information is provided for those new to hobby hydroponics and those who might want to try a different system. In some cases the information might not be relevent for use in a commercial operation.