I have a hanger i need to install rain drainage system, note the rain in the area is medium. Dual areas total of 6000 m2 will collect water. Each area 3000 m2 will have a downward 9.5 meter 6" pipe every 10 meters and goes horizontally 10 meters for the main outlet pipe. both 3000 m2 area would use the same outlet line. This mean that the main outlet line would collect the water coming from the 6000 m2. Note I'm considering slope of 2 cm/meter because the total length of the main outlet pipe would be 150 meters. Please advice regarding the main pipe.