Replace or Repipe?

Dave_61

Alex, I was rereading your email and have a couple questions on

the storage tank I will be purchasing. It is a Rheem ST80 with 2" boiler tappings at the bottom and a 2" hot water output on the top as well as a 1" and 3/4" opening (both on top).
I just want to do a walkthrough of the system and its necessary parts...
1. Water exits buffer tank at 2" outlet near bottom of tank and flows through 2" pipe to Taco 0010 with an integral check valve which pumps water into boiler inlet. Water flows through boiler and then out through 2" pipe to bottom of buffer tank (other 2" connection). Does return pipe to buffer tank need checkvalve if the Taco already has one where water flows into boiler?
2.Water for system exits top of tank (2" connection and then steps down to 1.5" existing header and passes through a spirovent before going to all existing pumps on header which is still capped at end). I wouldn't think we would need any other pump or checkvalves since each of the 007's would be pumping as needed and all have flowchecks on them.
3. Water returning from house would come from existing 1.5" manifold and enter the top of the tank through both the 1" T&P on top. Would there be an issue with flow if I just use the 1" T&P connection alone for the return header? Or would I have to use both the 1" T&P tap plus the 3/4" drain at bottom?If so, would I just tee them together? Would I need any checkvalves in this return piping (say in the 1.5" pipe) to prevent water from flowing back into the returns?

I have a Phase III TR-60 indirect which is on the existing manifold but only holds about 8 gal of boiler water, so i wouldn't think leaving it in the manifold would decrease its efficiency much.

I assume my primary loop with closely spaced tees would be totally dismantled with the above setup.

Does this all make more sense and make for a cleaner installation?

Thanks.
Dave