Torricelli's Theorem formula:
  v = √2 * g * h
where:
v: Fluid Speed at the Orifice, in meter/second
h: Height of the Orifice to the Top, in meter
g: The acceleration due to gravity, is 9.80665 m/s^2

Torricelli's Theorem suppose that a tank contains liquid and is open to the atmosphere at it top. If an Orifice exists in the tank at a Height h below the top of the liquid, then the speed of outflow from the orifice is √2gh, provided the liquid obeys Bernoulli's equation and the top of the liquid may be regarded as motionless.