how do self-filling/gravity fed pet water bowls not overflow and spill everywhere?

Question

how do self-filling/gravity fed pet water bowls not overflow and spill everywhere?

In: 276

Answer 1

The atmosphere is just that heavy. It’s shoving down on the surface of the water bowl at 14 pounds per square inch. The upside down bottle lets water flow out until enough water is in the bowl to block the bottle opening. At that point, air can no longer flow in and replace the lost water.

You now have a situation where 14 psi of pressure is pushing down on the surface of the water in the bowl and a vacuum being formed inside the bottle.

If you were to punch a hole in the bottle, air would be able to enter and fill the void and all of the water would spill out because there would be 14 psi inside the bottle as well as outside.