The system works. Here are some tomatoes I have grown in 5 gallon containers and in the double container resevoir system. If you want to learn more ...
Wow! A lot of words to say two five gallon paint buckets put together so you have a back-up water resevoir in the bottom. Tomatoes will grow really well in containers but you can't let them dry out even for a day. I recommend a 5 gallon bucket or larger. It is really hard to ensure you don't let container tomatoes dry out. You want to give yourself three advanatages. The first is using a 5 gallon container or larger. The second is using a moisture control soil mix and the the third is using this dual container design.
Step 1: The Basic Materials: 2 Five Gallon Buckets, Stones and Moisture Control Soil
The 5 gallon buckets will cost you about $4 each from any home improvement center. Different centers have different colors. You will need a bag of pebbles, the size in the picture. They can cost anywhere from $4.99 to $6.99. It will however supply enough pebbles for 3 or more containers. The soil can be store bought or hand made. The key is a lot of peat moss or other organic matter that will hold water. Any of the commerical bags of moisture control garden mix while work well. The cost for a large bag is about $9.99 and that should be enough for 3 or more containers.