Need solution for controlling supply from single motor to multiple building overhead tanks

Required technical solution with respect to type of pump, and other control system

A 7.5 hp motor supplies to 06 number of G+3 building overhead tanks. At times, when few (say 04) buildings overhead tank are full, the pipeline system and motor gets pressurized due to supply to only 02 buildings. The pipe line is 2.5 inch dia. I have heard, variable speed motor may be helpful. Also, if someone can suggest auto shut/open system for such arrangement where there is supply from one motor is to 06 buildings.