DWC – Deep Water Culture Hydroponics

In previous posts we talked about hydroponics using coco coir as a growing medium. This makes the gardening experience more like traditional dirt farming except we had to add a nutrient solution because the coco coir doesn’t contain any of the nutrients in normal soil.

What if gardening with dirt isn’t really your thing? Well, in this post we’re going to talk about an alternative called Deep Water Culture (DWC).

From Wikipedia, Deep Water Culture is “a hydroponic method of plant production by means of suspending the plant roots in a solution of nutrient-rich, oxygenated water.” (https://en.wikipedia.org/wiki/Deep_water_culture)

This is similar to using coco coir in that we still need to add a nutrient solution, but in this case the plants are sitting in net cups suspended above the nutrient solution with no dirt in the mix. The roots will grown down into the nutrient solution and get what they need from there.

The advantage to this form of hydroponics is you don’t really need to worry about watering the plants. You just change the solution every week or so and make sure the PH of the solution stays in a range of 5.5 to 6.5

Here’s how to setup your Deep Water Culture.

Supplies you’ll need:

Here’s the plastic buckets I’m using:

I randomly walked by a 3 pack of these at Home Depot for $4-$5 and decided to pick them up to try for hydroponics. I used a can of black spray paint to paint the bottom black and I taped off a small section so I could see the water level. Side note: if you decide to do this, don’t make the mistake I did. I didn’t sand the plastic to rough up the surface. As a result, the black paint flaked off of the bottom as I dragged the bin back and forth on a table. I put on some felt pads to avoid losing more paint.

Felt Pads in their packaging along with felt pads applied to the bottom of the plastic contianer
I used Felt pads to lift the container off of the table so I wouldn’t lose anymore paint.

Next thing we’ll need are net cups. I went with these 2″ net cups from amazon: https://www.amazon.com/gp/product/B073WJFHQH

To prepare the lid of the container, I traced around a net cup of either side of the lid. Since I didn’t have a 2″ hole saw bit, I used a utility knife to cut about 1/8 to a 1/4 inside the line I created. Then I test fit the net cup and slowly evened up the hole and made it a little larger so the net cup would fit. The end result was this:

Holes For Net Cups and Air Tubing In Lid
I cut holes in the lid for two net cups and drilled a hole on one side for the air tubing that I’ll use to deliver bubbles to the roots

You’ll also notice I drilled a hole in one side. This is for the air tubing for the air stone. More on that later.

Next, since the lid is a little light colored, I covered it with foil and tucked it underneath. This will keep as much light from reaching the roots and nutrient solution. Light can cause algae to grow and cause issues with the roots.

Lid Covered With Foil
I covered the lid with foil to prevent as much light from getting to the surface.

After that I cutout the holes again, this time from the foil

Cutout Holes In Foil
I cutout the holes from the foil.

Now it’s time to fill up the bin! I filled the bin about 1/3 of the way to the bottom of the net cup with the 1 teaspoon per gallon of nutrient solution I’d previously mixed up in a 5 gallon bucket, and filled the rest with filtered water from the fridge. I wasn’t as exact as I should have been and I just eye-balled it though. I put one netcup into the lid and used the other hole to pour the water in. I stopped filling when the water just reached the bottom of the net cup.

Water Touching Bottom of Net Cup
I filled the water in the bin until it was just about to spill up into the net cup.

Another mistake I made that I didn’t realize until a few days later is I didn’t check the PH of the final solution. I’ve been using tap water or filtered water from the fridge, and my water tends to have a higher PH. I set the PH of my nutrient solution to around 6 (the goal range for most plants I’ve heard is 5.5-6.5) when I mixed up a big batch of it but I didn’t check the solution after diluting it. When I checked a few days later I was up to 8-8.5 PH! Here’s why that’s important.

Nutrient availability at different PH levels. As we can see, the best PH for the most nutrients is from 6-6.5.
This image is from Wikipedia and is unmodified.
CC by 4.0
https://en.wikipedia.org/wiki/PH#/media/File:Soil_pH_effect_on_nutrient_availability.svg

The thicker the line, the more available that nutrient is at that PH on the chart. As you can see, the majority of nutrients are the most available at a PH of 6-6.5. What happened in my case when the PH was 8+ is the leaves on one of my lettuce plants started curling inward. I’m still waiting to see how the problem corrects itself now the that PH is right.

To check the PH of your nutrient solution, there’s a couple of ways to go about it. The more old school way is to use a PH test kit. This is the kit that I have: https://www.amazon.com/General-Hydroponics-pH-Control-Kit/dp/B000BNKWZY. The downside to this is it’s a bit more labor intensive and a little less accurate. You’ll have to collect a bit of your nutrient solution, drop 2-3 drops of the test indicator fluid and compare the resulting color to the chart.

The alternative is an electronic PH indicator. This is similar to the one I have: https://www.amazon.com/Accuracy-Measurement-Swimming-Aquariums-Hydroponics/dp/B0834S7G7P. It takes a little more care than the PH test kit in terms of keeping it clean and calibrated, but it’s easier to check the PH of your solution, and it’s easier and faster to read the current PH with the digital display.

Now that we have our PH under control, let’s setup the pump and air stone. Here’s everything I used. I bought all of this at my local pet store but I’m sure you could find it online as well.

Air Stone with Pump, Check Valve, and Airline Tubing
I use a small air pump with airline tubing running to a medium air stone to deliver air to the roots in the nutrient solution. I also used a check valve to prevent water from back-flowing to the pump.

I cut a small amount of air line tubing about 4-6 inches in length to attach the check value to the pump. This prevents water from flowing back to the pump if the power goes out.

The Air Line Tubing is easy to cut with scissors
Check valve attached to pump using air line tubing
I attached the 4-6 inch section of air line tubing to the pump and then to the check valve

I cut a longer section of tubing, about 2 feet in length, to attach to the other end of the check valve. I ran the other side through the hole in the lid and connected the air stone.

Attach air stone to pump
I cut a 2 foot section of air line tubing, ran it through the hole in the lid and connected it to the air stone inside the lid and the check valve on the other side.

Now that everything is connected we can drop the air stone inside, position it in the middle and close the lid. Once you plug in the pump, you’ll have bubbles!

Time to plant!

I started my seeds in a seed starter tray in these rapid rooter plugs: https://www.amazon.com/General-Hydroponics-Rapid-Rooter-Replacement/dp/B0002IU8K2. I suspect you could skip the seed starting tray and start the seeds right in the net cups but I haven’t tried that yet.

I put my seedlings into the net cups and used clay pebbles like these, https://www.amazon.com/xGarden-LECA-Expanded-Clay-Pebbles/dp/B01LZQBV33, to support the rapid rooter plug so it stayed upright. Be sure you rinse your clay pebbles before you use them, they can be pretty dusty in the bag and you don’t really want all the pebble dust in your nutrient solution.

I used clay pebbles shoved down the sides to keep the rapid rooter firmly in the net cup and upright.
I used clay pebbles shoved down the sides to keep the rapid rooter firmly in the net cup and upright.

I also covered the top so algae wouldn’t form and so light wouldn’t reach the roots.

Use clay pebbles to cover the top of the rapid rooter. This can also help keep the plants upright if they’re a little leggy from not having enough light.

There we have it! Now you just have to monitor the plants and wait. I’d recommend checking the PH level occasionally and I’ve heard that you should change the nutrient solution weekly. Changing the solution weekly also gives you the opportunity to adjust the strength of the nutrient solution from 1/4 strength for young seedlings to full strength for full grown plants.

I hope this guide was helpful in getting your own hydroponic setup going. Feel free to ask any questions in the comments section down below. Also, consider signing up for our weekly newsletter to keep up to date on our latest progress in our journey to become self sustaining!

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