Under Current / RDWC
Under Current or Recirculating Deep Water Culture (RDWC) systems: Plants sit in net pots with clay pebbles above large nutrient filled bins with the roots hanging into the aerated nutrient solution. The bins are linked together most commonly using a large diameter PVC pipe. A pump is also added at the front of the system that pulls water through a line from rear of the system into a control bucket. This return line generally has a filter on it that cleans particulate from the water before it reaches the pump. The individual bins, including the control bucket are aerated.
The system is kept filled from the reservoir by means of gravity and float valve with straight water. Because the system is linked together, adjustments can be made to the pH and EC through the control bucket allowing the operator to save time and maintain consistency in the nutrient solution. The system must be keep clean and the solution must be kept below 21 Degrees Celcius to avoid pathogens and root issues. In summer a chiller unit may be needed. Under current systems can give some of the highest growth rates and yields with the lowest maintenance of any hydroponic systems.