Tuesday, November 17, 2009

How To: Building a cheapskate DWC system

Here's a super-cheap hydroponic DWC (Deep Water Culture) system that I use to grow lettuce and start seedlings of all kinds. Some people call this a 'bubbler' system. In this type of system the plants live in little net pots that are inserted into the top of the system and the roots hang down into nutrient solution. It's a very simple type of arrangement, but very effective.

This system is excellent for germinating seeds and starting new plants, but it's also great for growing simple crops like herbs and smaller varieties of lettuce from start to finish. Another nice thing about this system is that doesn't take up much space- I keep mine on the floor in a closet.

Since it is so cheap and easy to build, I'll briefly describe how to build your own.

First, we'll talk about the materials you'll need:

(Item prices are in U.S. dollars.)

1) One 10 gallon opaque plastic storage tub (Rubbermaid or similar). Ensure that the container is wider than it is tall or you won't get as many plants into the system as you want. This should cost about $7 at a department or discount store. Note that in this photo I have already cut the holes that I need for the 2 inch net pots to rest in.

2) One large airstone. As you can see in the photo I like the flat, round type because they produc a very fine stream of bubbles and tend to stay in one place inside the reservoir. A round one like this costs $8, but you could easily use a 12 inch 'bar' type airstone which you can get at an aquarium or hydroponics store for around $3.

3) One 800-1000 aquarium air pump. This should cost around $7 at a pet/aquarium store.

4) Silicone airline tubing. I prefer silicone type to the regular plastic airline because silicone airline tubing is much more flexible and tends to go where you want it, not where it wants to go. $3 at a pet/aquarium store.

You will also need several 2-inch net pots [shown right] to hold your plants. You can get these online or at a local hydroponics shop and they usually cost less than 25 cents each. All told, you'll probably spend less than $30 on parts.

Now, to assemble the cheapskate DWC system:

1) Place your 10 gallon container into a bathtub, add a very small amount of dish detergent (not soap - use detergent). Fill the container with warm water and leave it to soak. Don't skip this step. You want the container clean of any residues from manufacturing that would otherwise get into your plants' water.

2) Using whichever method you prefer, mark spots on the lid of the container where you will be making the 2 inch holes to hold the net pots. I get 15 well-spaced sites onto the lid of a Rubbermaid 10 gallon container.

3) Using a drill and 2-inch hole saw (or a hobby knife and a lot of patience), cut out 2 inch diameter holes on all spots that you have marked.

4) Dump the soapy water from your 10 gallon container and rinse it VERY well. Leftover detergent would be very bad for your plants.

5) Bring the container and place it where you want the system to live. These containers become very flexible when filled with water and I don't advise trying to move them after they are filled.

6) Cut a length of airline tubing that is long enough to reach from the airstone (which will be resting in the bottom of your container) to the air pump. Connect the airpump and airstone to the airline and plop the airstone down in the bottom-center of your container. Don't start the air pump yet.

7) Add water to the container. The idea here is not to fill the container, but to add enough water that the bottoms of the net pots reach just barely below the surface of the water when the lid is in place. If you prefer, you could put the lid on the container now, place a couple of net pots in some of the holes and add water through one of the empty holes and simply stop adding water when the level of water comes over the inside of the bottoms of the net pots. (NOTE: For the 10 gallon rubbermaid container shown in these photos, this amount works out to be seven gallons of water).

8) Fire up the pump! Your contraption should look something like this:

If you look carefully (or look at the larger version of this photo) you'll see the bubbles bubbling away down in the reservoir. All that's left now is to add your favorite nutrient to the water, pH balance the nutrient solution and add your net pots and plants! I personally use Rapid Rooter plugs to hold my seeds and seedlings in the net pots.

If you have space near a nice sunny window, you could place your DWC system there and not have to worry about providing additional light. I don't have such a window so I provide artificial light using a 125 watt Hydrofarm brand compact fluorescent grow light.


  1. What do you put in the netpots to hold the seeds? Thanks I am going to get an airstone this weekend & get started as I am sorely missing my summer lettuces, kale & swiss chard1. Mari

    1. Hi Mari,

      I use Rapid Rooter plugs to hold the seeds. You can buy these online or in most local indoor garden shops.

      It might be easier to find "peat plugs" or "peat seed starters" at a local hardware or garden store. You might want to try those, too.

      Good luck!