Flood & Drain Advice

Which growing mediums?

The growing media you use with the flood and drain systems comes down to personal preference. Excellent results can be achieved with many different growing media's, but the key features you should look for are:

  • Low-medium Water Holding Capacity (WHC)
  • High Air Filled Porosity (AFP)

Clay pebbles

Clay pebbles are an ideal growing media for flood and drain systems as they don't require anything to be added or mixed in. Clay pebbles have good water retention and plenty of air space between them, creating a high air filled porosity.

Clay pebbles allow flood and drain systems to be flooded more frequently than other hydroponic systems, with a low risk of over watering. This frequent feeding cycle allows the oxygen in the rootzone to be replenished more often, leading to greater nutrient uptake and bigger yields.

Ebb and Flood Hydroponic Systems

Coco / Clay pebble mix

If using a coco / clay pebble mix, the percentage of coco should be 25-40% of the total volume of the growing media. Adding coco will allow more time between feeds which means fewer feed cycles per day.

Environmental considerations

Whilst EC and pH tend to remain stable in DWC systems, it is still important to check them frequently to monitor any fluctuations that may be occur and rectify them quickly

As with all hydroponic systems, the nutrient strength and feed cycle should reflect your environment. For example; if you're using clay pebbles and the environment is hot and the humidity is low, these hot and dry conditions will cause the plant to use more water and less nutrient, causing the nutrient strength to rise in the reservoir. In these circumstances we recommend setting the nutrient strength lower than usual to account for rising strength. In these conditions the pots should be flooded more often, up to once per hour.

The same room during cooler conditions, with a higher humidity, will mean higher nutrient strengths can be used and the number of feed cycles can be reduced to once every 2-3 hours. Always consider the effect that the environment will have on your plants and adjust your feeding strategy accordingly.

Understanding the flood cycle

To get the best possible results from a flood and drain system you must ensure you get the flood cycle right. The flood cycle is made up of 3 elements;

  • Flood Frequency - This is how often you flood the system, which depends on the growing media you’re using and how well established your plants are.
  • Flood Height - This is how high the water rises, in most cases we would recommend flooding to the maximum height.
  • Flood Duration - This is the total time of each feed cycle and will depend on the system being used, number of pots in your system (if applicable) and the growing media being used.

These key factors are play an important role in getting your feed strategy as accurate as possible.

IWS Flood and Drain

Planting in your flood and drain system

When planting into your flood and drain system, make sure your young plants are planted 1-2 cm into the growing media at the maximum flood height. This will allow the growing media the plant was propagated in to soak up the nutrient solution.

Please note: If your plants are too deep in the flood and drain system they will become saturated causing poor initial root growth.

Setting the flood frequency

How often you flood the system will be determined by the following:

  • The growing media.
  • The plant size and water requirements.
  • The environmental conditions.

If you are using a growing media such as clay pebbles you can flood your pot more often, if using a coco and clay pebble mix the flood frequency should be reduced.

The propagation environment will be quite different to the growing environment, most people find when moving plants into their growing environment their water demand will increase due to higher temperatures and lower humidity. It is important to make sure they do not dry out, or stay too wet between feed cycles.

Once there is noticeable increase in vegetative growth you can increase the feed frequency. As plants get bigger and their demand for water increases you will need to adjust the frequency.

A lot of growers consider 3 hours to be the maximum flood frequency but larger plants in a hot and dry environment may benefit from a flood frequency of once an hour.

During each flood, water and nutrients are delivered to your plant and stale oxygen is expelled. And with each drain cycle fresh oxygen is pulled into the air spaces in the root zone. So more frequent floods means more fresh oxygen around the roots.

Hint: During warm dark periods you may consider having 1 night time irrigation, this is only really necessary if using clay pebbles.