I have a 34' x 38' low pitched garage roof that gets almost full sun. I would like to buy several hundred feet of heavy black garden hose and snake it back and forth on the roof. Then, install an indirect water heater to front-end my regular water heater, and pump water round and round through the tank coil and the hose during the day when the sun is shining. Non-freeze months only, of course. I would take the whole thing down come Fall.
(1) Do I need an expansion tank on the hose circuit, or can I get away with just under-filling the circuit a bit?
(2) What should I use for a pump, and where would I get one?
Opinions and warnings are welcome, along with the above information!