Colander Design using One Bucket (click on pictures to enlarge)
A) colander (plastic and approximately 10 1/4" in diameter)
B) 1" PVC (24" in length)
C) 5-gallon bucket (only one is needed)
D) 1/2" poly irrigation pipe (2' length)
E) plastic cutting tools (Best: Drill with 1 3/8" & 3/4" hole saws, Alternative: razor knife, metal shears)
4 Easy Steps to Build
1. Go to a discount store (eg Dollar Tree) and buy a plastic colander with an approximate 10 1/4" diameter (10 1/4" is the width at the bottom of a typical 5-gallon bucket) for about $1.00US. Cut the protruding handles (if any) off the colander.
2. Watering Pipe. To get water into the reservoir use a 1" PVC pipe, 24" in length. With a 1 3/8" hole saw or another cutting tool, drill or cut off 3 or 4 of the plastic strips in the top or near the top of the colander. The watering pipe will go into this hole down into the reservoir. Cut a notch in the end of the 1" PVC pipe so water will easily flow into the reservoir.
3. Firmly push the colander (upside down, like an upside down bowl, so it forms a dome) into the 5-gallon bucket until it reaches the bottom. If it's a tight squeeze, you can cut small inverted V shaped notches in the colander's rim so it can flex and fit better.
4. Water Overflow / Air Holes. You'll have to create a water overflow/air "tunnel" from inside the colander out through the potting mix and out through a hole on the side of the bucket.
Drill a 3/4" hole in the side of the colander about 1/2" to 1" below the top of the colander (see picture with water dyed blue). Next drill a 3/4" hole on the side of the bucket at a height so the poly pipe will be horizontal. Stick a piece of 1/2" poly irrigation pipe (you could alternatively use a McDonalds or similar drinking straw with smaller holes) through the hole on the bucket's wall and into the colander's dome. There should be about a 1/2" to 1" of air space in the dome above the drainage/air pipe. This will provide a layer of 1/2" to 1" of air for the plant's roots. The pipe will serve as the overflow drain and air path. You want to get air in, and excess water out. You may want to repeat this step with a pipe and hole on the other side of the bucket, as seen in the picture, so you'll have a backup air/water overflow hole in case the primary pipe clogs or fails.
You're done! Just fill with potting mix and plant as described in our videos. As you fill the bucket up with potting mix, firmly pack down the potting mix (like in our planting video) surrounding the colander so water will wick well.
Advantages/Disadvantages/Thoughts: Cheap, about $4.00 to $5.00 US. Only one bucket is used and your time spent drilling holes is reduced by 75%. Like the traditional Global Bucket, it does take a lot of time gathering the materials and setting up, but there should be a time saving over the traditional Global Bucket. This colander system will have a smaller air surface for aeration that the traditional Global Bucket. If there is too much wicking (ie soggy soil) for your plants, you can drill a hole(s) in the side of the bucket below your existing poly pipe hole. This should lower the height of the water level and thus a reduction in the wicking area, but your reservoir will be reduced.
Automatic Watering (like in our irrigation videos): Run the 1/4" tube down the fill tube into the reservoir.