ABANDONED. YA about three tiers of society

[Kimm]

years ago, my teenage son read a book about a society that has three tiers. he believes they are rings. the bottom ring is the recycling, the middle are the gardeners and the top are the well off society. if the gardeners revolt then the top ring turns off the water.
sorry that it's just bits and pieces but it was many years ago that he read it.

[Sue]

This sounds like the Atherton books by Patrick Carman.
House of Power is the first one.

[Kris]

Sue's suggestion of The House of Power looks promising.

One reviewer on Amazon says, "Edgar's world is shaped sort of like a three-leveled top. The top level, the Highlands, are populated by the well-to-do people. They control the water for all of the other levels. If you fell off of the Highlands, and didn't die, you would land on the middle level, Tabletop, which is the level Edgar lives on. They are the workers who harvest food and raise animals. They receive water based on how well they feed the people above. If you fell off of Tabletop and weren't killed by the fall to the Flatlands, you would either be eaten by the monsters that live there, or die of starvation. If you could survive long enough to fall off of the Flatlands, you would fall off of the earth."

[Emily]

The Mortal Engines books may be of some interest, though I don't think that they are the right books for what you are looking for. They share some of the same elements, however, and I would definitely recommend them.

[Lobstergirl, au gratin]

Kimm left the group. Moving to Abandoned.