Thanks for the reply Glenn, I do plan on using solar evacuated tubes that this system would be a backup for, but possibly not right away depending on what the budget works out to be at the time. I was also thinking drain back system with a pump powered by a little solar panel so when the sun was out it would kick on. I wanted to put the RMH and water storage in the basement and the solar tubes on the roof or something, but it seems like that would be too far away from the water storage?
So I had pretty much thought against a closed pressurized system for sake of safety, but you mentioned it, is it possible to do it safely? I really would much rather have it closed in a perfect world, I just didn't think I should.