Cold water is drawn from the pool via the pool pump to the sand filter. Your current pool pump configuration will lead the water back to the pool once filtered. When solar panels are installed, this is the stage where a riser pipe is led to the panels situated on the north facing roof. The panels outlet will lead back down and connect with the original pipe leading to your pool. The water will keep circulating as long as the pump is running. The heating cycle can be isolated by closing the valve between cold and hot water pipes.