1. Formula

2. Time to empty a tank

Toricelli formula is applied to
calculate tank orifice flowrate

Q=Liquid flowrate at orifice (m3/s)

C=Orifice coefficient (-)

A_{1}=Orifice area (m2)

h=Height of liquid from top of tank to middle of orifice (m)

g=gravity acceleration (m.s^{-2})

g=9.81 m.s^{-2}

C=0.6 for non profiled orifice

t_{v}=Time in s to discharge a tank up to the level of the
orifice (s)

H=Height of liquid at t=0 (m)

**Source**

Mecanique et Rheologie des fluides en genie chimique, Noel Midoux, Lavoisier Tec et Doc, page 51