Flood Floors


How Does Your Flood Floor Work?

The Recipe Tanks:

Your system has been designed with 3 recipe tanks that you can fill up with the pre-made solution of your choice. Typically these tanks a re filled with a high E.C., a low E.C. and a fresh water solution (feed 1, feed 2, feed 3,). These tanks have a capacity to hold approximately 4 floors of water so that we can continue watering without waiting for water to return. Each tank has two float sensors in the tank, or perhaps one pressure sensor.

If they have floats they are positioned in such a way the one will be set high in the tank and one will be set low. These sensors are for your fertilizer top off. The low one will open the valve from the fertilizer system to begin topping off the tank and the upper will shut the valve off. If you have chosen the pressure type of sensor for your system you will run it the same way through your computer based on percentages of empty and full.

Be careful that the top sensor is not too high as you maybe filling the tank and the possibility or return water coming home may overflow the tank.

The Flood Pit:

This tank has two large pumps in the bottom of it. If you look at the bottom of this pit you should notice 3 large air actuated butterfly valves along the walls. These are the valves that access the recipe tanks. When a floor is asked to run the recipe valve of your choice will open and flood the pit. When the flood pit sensor sees that there is now enough water in the flood pit, the pumps will turn on. These pumps are high volume at low pressure and are large enough to move a can of soda (so please watch your toes).

Recipe Changes:

You will notice at the top of the pit you will see a smaller air actuated valve that flows into the drain pit. This valve is your transfer valve. When you are done with a recipe and wish to change recipes there is an amount of water left in the flood pit that you do not want. So after the last floor valve is done running, the valve on the floor closes, the recipe valve in the flood pit closes and the transfer valve opens to empty the pit into the drain pit so that we can start fresh with the next recipe.

You will notice that the pumps are recessed into the floor; this feature allows the flood pit to be emptied as much as possible between recipes. Now with the new recipe in the tank we will first need to rinse the main lines. This is done based on time. With the rinse valve open the computer runs the pumps for a pre set time to flush the old recipe through the rinse valve at the far end of the system retuning it to the drain pit, through the filter, and back to the original tank. This total process takes approximately 20 minutes. Now you can start running the floors with the next feed.

The Drain Pit:

Now we have water returning from the floor. This water will drain via gravity into the drain pit where two pumps are waiting for it.

As soon as the water level in the drain pit activates the level sensors the pumps will turn on and begin to drain the pit. If the floor system is running steady these pumps should not shut off till the end of the cycle. The water is pumped over the filter and again through gravity it will flow through an above ground line and pour back into the tank you selected, and the process starts all over again.

The Filter:

If you have gone on our recommendation you have purchased a cloth filter. This filter comes standard with our .5 oz polyester cellulose material. This cloth will filter to 20 micron and the filter will move the cloth itself when it sees that it is plugging up. The cloth becomes wasted once it has been used. You will go through a large amount of cloth on start up when the entire fine concrete dust and construction soil gets flushed from the system. After this initial start up your use will decrease.


When the floor system is not in use (at rest) any over head hand, boom watering and even gutter drip that ends up on the floor will return to the drain tank. The tank will slowly fill and than the pumps will start, but where does that water go? Your system has been designed with a drain or dump valve. For the sake of the computer it might see it as a fictional tank 4. This valve has been hooked up to flow outside the greenhouse and run off into a waste area. This valve has been put in place so that you have a way to release unwanted water. Weather this water comes back from drain or weather it is a result of unwanted recipe you need a way to get rid of it hence drain valve #4

Sizing and Specs:

When your system was quoted the type of design, tanks sizes, filter size, and flow rates where recorded. Please review your quote to get these answers.

When Growing NFT Lettuce:

This is a special feature of your floor. When the time comes for this crop the rubber barrier that is between two floors will need to be removed. We have provided approx. 5” long PVC Gasketed pipes that will need to be installed into the drain holes. With these pipes installed you are set to start filling the floor.

The floor is designed to hold 4” of water depth on the concrete curb (approx 5.5” in the center of the floor). When the water level reaches the top of the Gasketed pipes the water will overflow into the drain and back to the drain pit (your floor is now full). With all the floors full you can now start to grow.

The floor is designed to add water in predetermined intervals daily. As water is added to refresh the floor old water will over flow the gasketed pipes to circulate the floor. Because the floor is now in essence a double floor you can add water from the valves on both sides to circulate the floor evenly.

This idea of how to run the floor in an NFT fashion is new to Zwart Systems we have not done it before. However we think we have covered all the challenges in a user-friendly design.

Cascading Flood Floors

The cascading style of flood floor has the water supplied on the high side of the growing area and running a ¼” to 3/8” depth across the floor. The water then runs immediately into the drain piping and is returned to the tank that supplied it.

It takes 30-45 second for the water to cross the floor and enter the drain line. This system allows the grower to water evenly across the crop even if he/she reduces the irrigation cycle to restrict the amount of capillary action if he/ she wants to hold back the crop.

Unlike the traditional style, unfiltered water never enters the supply line. The drain line does not require any valving as it is always open. Since water begins to return almost immediately to the tank system, smaller tanks can be used and there is little to no time between watering floors.

If you intend to grow a smaller (6” and under ) pot ,tray liner, propagation or rockwool cube, this is the system to choose.

Traditional Flood Floors

In the traditional style the growing area has concrete poured in a shallow “v” shape that fills and drains to the centre of the length of that area. The centre of the “v” is usually 1 to 1 ½” lower than the edges. Water is pumped up the buried supply until the depth at the top of the “V” has been achieved. It is then allowed to drain through that same supply pipe back to the tank from which it came.

Typically, this system requires about 5 minutes to fill enough water to that the pots on the edges are in 1 1/2 “ of water and 7 minutes to drain away (this varies due to floor size and pump sizing) the capillary action of the plants only allow them to draw up what is required to reach the saturation point of it’s media even though the plants in the centre of the floor are in water much longer than the edges.

They should all achieve an equal amount of water in the pot if given enough time for that action to be completed. This style of floor has an advantage for growers of larger pots and/or nursery stock because of the depth of water than can be achieved.

Flood Floor Construction

The quality of a flood floor starts in the very first stages of construction. Zwart Systems works very closely with Al Brower of Tradewind Construction. A Zwart Systems consultant will begin with the customer to determine what type of floor is right for them. After this decision is made and the quote is accepted Zwart will look after the scheduling of the project and provide a complete project for the customer.

  1. It all begins with taking elevation shots.
  2. Remove or add soil as required.
  3. Then some excavation for the mainlines and spur lines takes place.
  4. Next a little laser grading to make the base exactly mirrored to what the finished concrete should be.
  5. Lay down some wire mesh and rebar.
  6. Tie down the heat tubing.
  7. Time to pour an even contoured 4” of concrete with a screed. (5” on the main walkway).
  8. Drill some holes and rubber barrier.
  9. Add water and plants.

If these 9 steps look easy, its because that’s how we make it look. A lot of engineering and planning goes into each project. If you need some budget numbers or would like to discuss if this system is right for you give us a call. We are always happy to chat about a project and if it fits your business plan we will make a site visit with all the necessary people to give you an accurate quote.

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