I have seen where guy had used five hundred feet of one inch black irrigation tubing, that he had coiled into a sprial on top of an arbor next his swimming pool. He then had hooked the filtration pump of the pool into the ends of the black irrigation tubing, and as the water circulated through the tubing it would absorb heat from the sun and raise the pool temp to 20* to 25* more than the ambient temperature of the surrounding air temperature. Just a thought. Jack