DIY EMT Solar pool heater

@famous bob How about ABS pipe? It's already black. If @pishta gets a few seasons out of it before the UV rays eat the pipe, he has achieved his goal and can replumb it. I know a guy who built an outdoor shower, and used the coiled black water line like pictured above. I understand Pishta wanting to use the foil underneath the pipe he chooses, to reflect heat to the bottom side of the pipe also. The guy I know with the outdoor shower pumps his solar heated water into an old water heater tank that is inside a box that is 2' bigger, and has sand poured into the box to surround the tank and hold the heat in. He is planning to upgrade that to spray foam instead of sand, to hold the heat in longer.