Everything about flood and drain systems for growing cannabis

Everything about flood and drain systems for growing cannabis
Max Sargent

The principle behind Flood and Drain systems for growing cannabis is very effective, yet very simple. Find out how it works at CannaConnection!

The principle behind Flood and Drain is effective, yet simple. The system uses a pump that floods your plants, sitting in pots or on a growing table, with a nutrient solution from a reservoir. Turn the pump off and the nutrient solution will drain back into the reservoir. You can set the frequency of this “flooding and draining” of your plants by using a simple timer that is attached to the pump.

Every time your plants are flooded, their roots will be submerged in the nutrient solution, allowing them to take up all the water and nutrients they need for rapid growth. One big advantage here is that the constant flooding and draining also ensures a steady flow of fresh oxygen. This greatly stimulates healthy and fast growth. As your plants grow bigger, you simply increase the flood and drain intervals.

What sets Flood and Drain Hydro apart from other growing setups is its flexibility. Flood and Drain can really accommodate to everyone. It’s essentially like an auto-watering system on steroids since it allows you to fine-tune the feeding intervals per day. This also makes Flood and Drain a good choice for experienced growers who want more tailored control over their growing environment.


Flood and drain compared to hand-watering

Soil and compost growers typically won’t water their plants every day. They will usually water every other day or even less frequently. Since a Flood and Drain is always “active”, nutrients will be reaching your plants more often. Providing them with less but more frequently supplied nutrients, spread out throughout the day, will promote better growth and increase plant health.

Flood and Drain also addresses the issue of oxygenating your root zones on a constant basis. When watering by hand, your plant’s root zone may become stale and depleted of oxygen for a day or sometimes longer. The Flood and Drain system constantly forces out the staleness around your plant’s roots and pulls fresh oxygen back in. Again, your plants will be healthier, grow faster and will ultimately have a much better yield!

The problem with some growing setups is that nutrient salts may start gradually building up in your growing medium. With Flood and Drain Hydro, any nutrients that are not used will simply drain back into your reservoir, addressing a major issue that can otherwise lead to all kinds of growing problems.


The two most common Flood and Drain setups make use of the same principle, although there are some slight differences. These two systems are the Flood and Drain Table system and the Modular or Bucket Flood and Drain system.


In this Flood and Drain setup, the plants sit above a nutrient solution reservoir that is shaped like a flat table, hence the name. This table drains the solution towards the centre where two fittings are located. One of these fittings, the inlet, is flush to the table. The other, the overflow drain, rests about 10cm high from the bottom of the table.

The pump connects to the inlet and the overflow drain goes back into the reservoir. The nutrient solution is pumped into the table through the inlet drain. When the level of the nutrient solution on the table reaches the overflow, it will flow back into the reservoir.

Once your pump is switched off, the nutrient solution will flow back down the inlet drain, into the reservoir.

The pump is controlled via a timer. This timer will allow you to set the frequency of the Flood and Drain intervals. Flood the table and your plants will get all the water and nutrients they need. At that time, the air around the root zone will be replaced by fresh oxygen as an added benefit.

The Flood and Drain Table system offers a major advantage, allowing you to grow in any type of growing medium, including clay pebbles, coco and even soil. Some growers prefer to keep their plants in pots that they then place onto the table. Others fill the table with clay pebbles so that the plant roots can grow anywhere on the table.

Compared to some other hydro setups, Flood and Drain Hydro is (pretty much) leak-proof, which makes it a great choice for apartments and urban growing. Commercially available Flood and Drain Table systems can fit perfectly in a standard sized grow tent or greenhouse.


The Modular or Bucket Flood and Drain system works pretty similarly. The main difference is that it doesn’t make use one of a single large table for the “flooding”, rather each plant sits in their own pot.

Each pot has a supply tube connected to it that leads from the bottom of the pot into a so-called control bucket. This larger control bucket is connected to the nutrient reservoir. The pump in these bucket-based Flood and Drain systems is only flooding and draining the control bucket. The solution is then supplied to the connected plant pots by gravity. The control pot makes use of magnetic valves which control the pump and flood level to prevent any over-watering or flooding.

One advantage of Bucket Flood and Drain Hydro is that you have more freedom to place your individual plants inside your growing space. This can allow optimal placement of each pot under your grow lights, letting you max out our plant’s growth and harvests. These modular systems are also easy to expand since you can always add more pots if and when needed.


Once set up, a Flood and Drain Hydro system makes things very easy for the grower and offers a high level of flexibility at the same time. This makes these hydro systems suitable for pretty much any type of grower, from the novice with no or little experience to the seasoned cannabis growing enthusiast.

Less experienced growers won’t have to worry about feeding schedules and watering since all of these are taken care of automatically. Only having to maintain a single nutrient reservoir frees up more time for maintaining a healthy growing environment.

Seasoned growers can use these systems to fine-tune everything to their growing environment and the strains they're growing. This allows them to maximise their yields.

Flood and Drain Table systems are especially suited for small-scale growers, that need an effective, active hydro system that will perfectly fit their growing space. Many Flood and Drain Table setups accommodate regular sizes like 60cm or 120cm which can make good use of standard sized grow tents.

For those who tend to grow more plants, bucket-based Flood and Drain systems can be ideal since they tremendously help cut down the time it would require to water and feed such a large number of plants. A smaller Table Flood and Drain Hydro system can still prove useful in addition to a vegging system for seedlings and younger plants.

It doesn't take a rocket scientist to operate a Flood and Drain system, once it has been put in place. It is likely though that you will want to make the best out of it. Shortly put, you will want to maximise your yields.

Seasoned growers recommend that you keep a record where you write down the number of floods per day, along with the amount of solution needed to top up your system.

You probably won't get an “optimal” number of floods and drains during your very first try, and that's okay. Don’t shy away from experimenting until you find what works best for you and your setup. It shouldn’t take long for you to find an optimal number for your daily floods and drains. Maximum growth and a massive harvest are at hand.


Many growers start their plants in rockwool cubes or in coco. Before you transfer your seedlings into your Flood and Drain setup, make sure they are root bound. As soon as you see plenty of white roots coming out the starter medium, your seedlings are ready to go into your hydro.


Flood and Drain doesn’t necessarily require that you support your plants, in contrast to other hydroponic setups, where there is no growing medium surrounding the roots. On the other hand, if you grow real monsters with some sizeable buds, you may at some point want to consider staking so that your plants won’t tip over.

Did we convince you about the many benefits of Flood and Drain Hydroponics? We're sold on the easy setup and maintenance that will let you grow some excellent bud before you know it!

Max Sargent
Max Sargent

Max has been writing about cannabis and psychedelics for several years now. With a strong belief that an open, honest attitude toward drugs and drug policy can improve the lives of many, he seeks to offer insightful and developed opinions on the subject.