The water solar heaters sound very effective. If it's possible to make them out of PVC I might have to look into that method. I assume they would require expensive copper, but if the PVC is painted black it makes sense that it would still capture plenty of heat anyway. I'll have to look into this system as well.
They worked out well enough. You can actually get black PVC that you wont have to paint. It was contained in a large "box" with one side being glass/plexi (that would probably cost the most). Ill try to find some links for how they were built. I was very young when my family was using them. This would have been back in the late 90's.
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