A recirculating hydroponic system collects the solution that passes through or around the roots and returns it to the reservoir. DWC, RDWC, NFT, ebb and flow and recirculating drip are all closed systems. Only what the plants take up or evaporate is lost, so water and fertiliser use falls sharply compared with drain-to-waste.
In practice
Because solution is reused, its composition drifts: the plant takes some elements faster than others, pH moves, and root exudates and microbes accumulate. Growers top up between full changes, check pH and EC daily, and change or refresh the reservoir every one to two weeks. Recirculation can spread root pathogens such as Pythium to every plant, so sanitation, cool temperatures and a deliberate microbial strategy (beneficial or sterile) matter.
Don't confuse with
- Drain-to-waste: each feed used once.
- Recirculating drip: one kind of closed system using drippers.
DWC (deep water culture) suspends a plant's roots in an aerated nutrient solution, typically in a bucket with a net pot lid and an air stone.RDWC (recirculating deep water culture) links several aerated buckets to a central control reservoir, pumping solution through all of them to keep conditions uniform.Ebb and flow (flood and drain) periodically floods a tray of potted plants with nutrient solution, then drains it back to a reservoir, pulling fresh air into the medium.Drain-to-waste fertigation feeds each plant fresh nutrient solution and lets the runoff leave the system rather than returning it to the reservoir.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.EC (electrical conductivity) measures how well a solution conducts electricity, a proxy for total dissolved salts; growers read it in mS/cm to gauge nutrient strength.A genus of oomycete water moulds, such as Pythium myriotylum and P. aphanidermatum, that cause brown, slimy root rot, especially in warm hydroponic systems.Drip irrigation delivers water or nutrient solution through tubing and emitters directly to each plant's medium, in measured amounts on a timer or controller.A reservoir is the tank that holds a system's water or nutrient solution, the place where pH, EC, temperature and oxygen are measured and adjusted.NFT (nutrient film technique) runs a thin, continuous film of nutrient solution along sloped channels, with roots resting in the stream and exposed to air above.
