Basic Fluids Question - How do you calc exit velocity of water from a nozzle ?

I am not a Fluids engineer by any stretch and was hoping that someone could
help or point me in the right direction.

I have a cylindrical pipe, 1 meter long and 0.02 m wide. It is verticaly
oriented
There are plates at the top and bottom of the pipe so that it is a closed
chamber.
The pipe is half full of water. The top half of the chamber is compressed
air (1000 psi)
At the bottom plate there is an exit hole 0.002 m in diameter.

What will be the exit velocity (mass flow of the water) ?
Can anyone help me ?

Many Thanks

s