Rocket Water Heater v.4

Fourth time is the charm? Maybe??? I am still working out dimensions on most elements. Some of it I don't think I will know until I begin construction. I am attempting to make the design somewhat modular so that the various tiers of the heater can be independently re-engineered as needed. Feel free to ask questions or point out mistakes as spotted. Thanks much!

Addendum: The open hot tank is designed for maximum surface area. I need to decide if I am just going to have a flat back or angled back to the tank to allow more airflow up into the tier 2 heat exchanger and exhaust manifold. I will have running water to top up the open tank as needed while the system is in operation. I also have considered a non-pressurized lid that runs to a condenser loop and back into the hot tank. If in the course of running it I find I am loosing too much water I will explore that idea further.