Draw a line bisecting one 5 gallon tub along the width. Make this line 4 inches from the bottom of the tub.
Cut this tub in half along the line using a utility knife. When the earth box is assembled, the lower half will be your water reservoir and the upper half will be your soil chamber.
Place the bottom of this tub face down on the lid, and trace around the edge.
Cut along this line to make the lid smaller. Discard the outer edge that you trim away. What is left will be a barrier to separate the soil chamber from the water reservoir.
Drill 1/2 inch holes in the lid using the drill and 1/2-inch drill bit. Space the holes every 1 inch in the bottom. Stagger each row of holes, and make each row 1 inch apart.
Place the open end of the PVC pipe against the lid and trace around it. Cut this out to make an opening for the PVC pipe. This pipe will allow you to pour water into the reservoir without having to pour it though the earth chamber.
Place the bottom half of your tub face-up in the location where you plan to grow your plants.
Place your four pieces of 6 inch wide PVC pipe in the bottom of the water reservoir. These will help to support the weight of the soil chamber. Space them as far apart as you can for more even weight distribution.
Place the lid on top of the PVC pipe.
Cover the lid with mesh window screen fabric. Cut the edges of the fabric so that it will fit over the top of the lid. Cut a matching hole in the screen to match the 3/4-inch PVC pipe hole.
Insert the 3/4-inch PVC pipe into the lid and the window screen so that one open end of the PVC pipe is in the reservoir.
Spread a thin layer of epoxy along the bottom end of the top section of the tub.
Press this section of the tub firmly onto the lid. Leave the tub alone while the epoxy dries and cures.
Fill the soil container with peat-based potting soil.
Plant your plants in the potting soil.
Cover the plants with a weed barrier cloth. Cut the cloth so that it fits around the 3/4-inch PVC pipe.
Cover the barrier cloth with a commercial mulch to prevent evaporation.