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

One side (the jug) is sealed air-tight. The other is open to the atmosphere.

As long as no air gets into the jug, air pressure is only pressing on the bowl surface, not the jug. Any air-space in the jug is at lower pressure than the atmospheric pressure of the surface of the bowl, and cannot not push the water down.

Now, poke a hole in the jug. Atmospheric pressure will push in, equalizing the pressure in the jug with the outside of the jug…the water will settle to one level (ie. go everywhere).