The right materials
Copper is the ideal material for conducting heat. However, copper is brittle, heavy, expensive, and subject to corrosion in chlorinated water. Glazed collectors (covered with glass) with copper tubing are also 10 to 25% less efficient for collecting heat because their bigger tubes offer less exposed surface to the sun than the smaller, tight-knit tubes of non-glazed synthetic solar collectors. However, they can be used almost year round if well inclined and properly sealed. They are more suited to domestic water heating which requires less energy than pool heating.
The solar manufacturers prefer synthetic materials for their durability, their non-corrosiveness, and their resistance to ultra-violet rays. Neoprene (also used as insulation for scuba diving), offers all of these qualities, but remains les efficient for collecting heat. Polypropylene (the yellow or blue plastic casing for natural gas pipelines) can be made much thinner, more conductive of heat, without sacrificing durability or resistance to ultra-violet rays. All plumbing, including the headers of the collectors should be made of PVC or polypropylene, never of ABS which is not designed for outdoor use.