Need info on the type of pipe GI or CPVC to be used to pump water from underground tank to overhead tank for a building in Delhi


I am constructing a 4 storey building with stilt parking in Delhi. I will be lifting water from underground tank of 2000 lts capacity (4 tanks) which are underground in stilt. Height at which 4 overthead tanks(1500 lts each) will be kept is 50ft. I will be using GI pipes.

Kindly clarify the following doubts

  • Should I use GI pipe or CPVC.
  • If I use GI then what should be the dia of GI pipe which should be used to lift water from underground tank to OHT (plumber suggested 1 inch)
  • What should be the dia of main lines coming from OHT to different floors (plumber suggested 1 inch)
  • What should be the diameter of diffrent pipes used internally in kitchen and bathrooms be (plumber suggested 1/2 inch). There are 2 bathrooms and 1 kitchen on each floor.
  • What should be HP of the submersible pump be
  • In summers water in OHT becomes very hot. Therefore from the line which is going from undergroundg tank to OHT ,I will install a "T" and 2 lines will be diverted to each bathroom for cold water in summer along.Will this effect in anyway?