Building a bucket system

Please see link...
Hydroponic Gardening, The Bucket System, Indoor Gardening and Hydroponics, Maximum Yield

I want to make the bucket system in the article above, but have a few questions.

Do you need to have the reservoir lower than the buckets? otherwise water is going to sit on the bottom of all buckets... ? Wouldn't this create root rot?

If all buckets including reservoir were on the same plain, the water would even out, not drain back into the reseroir.

How I can solve this problem &/or improve on this system....?