System pressure determination for pressurization tank sizing

[nevinjohn]

After performing the pressure drop for chilled water system, assume 50m head for the pump. Now, to size the pressurization tank how do I get the system pressure? I am sure, this is not the same as the calculated press loss. Since its a closed piping system I am confused if I should be considering the building height to size the tank?, considering P = density X g X height?

Now, for the above lets say we have a very tall building (more than 100m). Shouldn't the pressurization tank be sized considering this height? What bout the FCU/AHUs at the basement of this loop? The pressure on this would be enormous. Can the balancing valve alone handle this?