Routing all roof level pipes to one outlet

[NandM]

I'm finally about to start the groundwork (yay!) and am thinking about the best way to get the rainwater to the soak away. I'm hoping my simple design by routing all the pipes to one outlet would work?  In effect the pitched and dormer roof to route down to the flat roof pipes on ground floor and from there to one gulley and then to the soak away at a distance of 5m, and under 4m of patio.

 

 

[Russell griffiths]

Have you worked out the fall on the pipe

by the time you travel across the front of the house then down the side, then across the back before turning out into the garden you could be a meter below ground. 
have a measure up.