# How much air is required to transfer liquid?

## Main Question or Discussion Point

Hi all,

I am trying to wrap my head around how much air is needed to transfer liquid from one tank to another tank. Here is a sketch of the problem

The valves at the bottom of the first tank opens up, and air is transferred to the first vessel to transfer the liquid completely to the second tank. The second tank has a vent to atmosphere. How do I figure out how much air is needed to complete the transfer process?

Thank you

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the volume of air will be the same as the displaced liquid, though it will need to be pressurized, and depending on how you define the volume (pressurized volume or atmospheric volume) you'll need to account for that.
the pressure will depend on the density of the liquid, and the height of the liquid will be from the bottom of the top "elbow" to the bottom of the tank (unless you drain the bottom elbow as well)

help_pls
the volume of air will be the same as the displaced liquid, though it will need to be pressurized, and depending on how you define the volume (pressurized volume or atmospheric volume) you'll need to account for that.
the pressure will depend on the density of the liquid, and the height of the liquid will be from the bottom of the top "elbow" to the bottom of the tank (unless you drain the bottom elbow as well)
Thank you so much! I think I got it.

Oh, I just noticed something else.. the area above the liquid will need to be pressurized as well, so thus the volume (at pressure) will of course be that of the entire vessel