Complex with 1200 flats looking at rainwater harvesting-Can we have a consultant to look into the issue of piping to help us out

(Query received over email from Ellen)

Hello,

We live in a huge complex of 1200 flats and are looking into the RWH system.
Is it necessary to separate the rooftop from non-rooftop water for:
a) Sumps
b) Injection wells (for borewells)
c) Recharge wells
It looks like the separation of these pipes will be messy. Also, if we would have a consultant who could look at this particular question (someone who works in piping), that would be very helpful.
 
Thanks and regards,