pressure

Are you refering to Torricelli's Law? Please give additional details if the following doesn't answer your question.

If a container is filled with water and closed, and an opening is made on the wall, near the bottom, we readily observe that the pressure at the opening or hole is atmospheric, while the pressure at the opening but inside the container is ρgH, where H is the height of the container upto which water is filled.

There will  be  fluid flow, if ρgH> Atmospheric pressure.

Other way if the container is open then the pressure at the opening but inside the container is Atmospheric + ρgH.

Regarsds,

Team,

TopperLearning.