Which is the best kind of pipe to replace the existing GI pipe in the apartment complex?

Hello,

I live in an old apartment complex in Bangalore that currently has GI pipes installed for all the plumbing. All external pipes leading to each apartment from the water chambers and internal pipes (in the bathroom) have GI pipes installed. As these pipes are over 25 years old, the apartment association would like to change all the external plumbing (leading to each apartment).

We are confused on the choice of pipes to be used.We have been suggested to use many different kinds of pipes. Would like to know which is most preferred one CPVC, GI, or PPRC?

Thanks,
Rakesh Ganatra
rakesh.ganatra@gmail.com