Kindly let me know how to calculate the capacity of the pressurisation unit the gpm and the head of the pressurisation unit and the selection if this unit is on the same level of the chiller and primary / secondary pumps if the volume of the system is around 9050 lts, any body can help me out in this.

Why to use diaphragm pressure gauge instead of Bourdon gauge.

Kindly let me know how to calculate the pressure vessel size,gpm and the head of the pressurisation unit, for using to fill the chilled water closed loop circulation system looses due to small leakage or some other cause.following are the details.
System volume 19 m3
Vertical hight 105m
Chilled water pump discharge 59LPS @ 4Bar