How to design the size and depth of drainage Manhole?

1- take tap point fromt the existing manhole

2- take tap point from pipes that came outside buildings

3- use slop 1% 

4- every 15 m make manhoe

5-the invert level for pipes depending on the entry and exist of pipe to manhole

how many in day , how much % every hour, how big % of dirty , where to go next(them self or by pumps, or pipe)