Looking at the diagram from the sungrabber solar heater installation manual, it shows that the panels should slope 1" per 10' for proper drainage. But it shows it sloping toward the filter and pump. I've added red marks to the diagram where I intend to have check valves. One is so that the flow can not go backwards thru the filter and the other is for when the system is bypassed so that the solar panel is not pressurized. To me, it seems that I'd want to slope the panels the opposite direction as shown. I'm in South Florida so am not worried about freeze protection, but I'd think it would be good to have the water drain when the pump is off.[attachment=0:3pf4dmhx]solar.gif[/attachment:3pf4dmhx]