Water addition under nitrogen atmosphere

My question is regarding the impact of the pressure generated inside a reactor, when adding water to it (talking about the production of oral liquids here).
The first step of the manufacturing process is the Inertization of the reactor (by adding nitrogen to the reactor until 0.5bar). Then I want to add Purified water.
The question is: since I have the vent filter of the rector closed, and the amount of water to be added is measured with the scale (by weight), is it possible that the amount of water weighted in the equipment scale is incorrect due to the pressure increase by the addition of the water?