I had ask You questions about this some time ago.
I have 3 16 story occupied buildings that were designed and installed in the early eighties. Two have standpipes only and the third one is sprinkled. All three are connected to one common fire pump.. The old fire pump needed replacing and when we applied for permit the AHJ says we have to raise the pressure to 139 psi at the required flow (500gpm) at the roof. Raising the existing over 70 pounds on a system that is over 30 years old almost and could require the system to be replaced.