How to figure drainpipe size?
I will be collecting water from 2 or 3 downspouts and sending it around the house to the street. I have enough slope but not sure what size drain pipe to use. I plan to use 3" corrugated pipe but would 4 inch be better? How do I figure how much each pipe can handle. My roof is about 1500 sq ft and this will be draining about half of the roof.