if abuilding is 12m high and the pressure needed at the top is 400kpa what is the required pressure at the meter?

Answer 1

12m of water ...
consider a m^2 surface, h high
weight of water=density*g*h*area
pressure from weight=density*g*h

pressure needed=400kPa+ 1E6kg/m^3*9.8N/kg*12m*1/1000 kpa

add them, and you have the pressure in kPa.