Torricelli's Tank (Draining Through a Hole)
Punch a hole in the side of a water tank and watch the jet arc out and the level fall — the jet speed depends only on how deep the hole is below the surface, and the tank empties on a curve you can predict.
What you can adjust
- Tank height (H)
- 0.5 – 3 m
- Hole height above floor
- 0 – 1 m
- Hole diameter
- 5 – 30 mm
- Tank diameter
- 0.3 – 1.5 m
- Discharge coefficient (Cd)
- 0.6 – 1
How tall the tank is. The tank starts completely full — the water level begins right at the top.
Where the hole is punched in the side wall, measured up from the floor. Must be below the tank height — draining stops once the water level falls to the hole.
A bigger hole drains the tank faster but doesn't change the jet's initial speed — that depends only on how deep the hole sits below the surface.
A wider tank holds more water over the same hole, so it takes longer to drain.
How much a real hole's shape slows the jet down compared to the ideal Torricelli speed. A sharp-edged hole loses the most; a smoothly rounded one loses almost nothing.