I found this thread during a search.
To follow-up, for a typical DIY thermosyphon system, what's the practical limit on the horizontal distance between the storage tank and the collector?
My house is situated on the side of a hill and I have full sun exposure, so I can easily locate my tank 2-3 ft above my planned collectors, but approx. 15 - 20 feet away (horizontal distance).
Assuming the slopes are all positive and 1" pipe is used, should this be a workable distance for a thermosyphon system?