How IWS Flood and Drain hydroponic systems work At the set times solution is pumped from the water butt into each pot allowing the plants to feed and pushing out air. Floats ensure the same level of solution rises into every pot. When the solution drains from the pots fresh air is pulled into the rootzone. The drained solution is pumped back to the water butt, rebalancing the pH and EC. Because stale air is replaced with fresh oxygen-rich air at every feed the roots are well oxygenated which drives more productive growth. Drainage is excellent with this grow system, so it is important to remember to increase the amount of feeds as the plants grow.