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 water in the bowl blocks any air from getting up underneath the feed and prevents any air from getting up into the container, so the water is held up be that negative pressure. Kind of like when you suck water you a straw and then can hold it there in the straw.

When the let drinks water, the water level lowers, allowing air up into the water container, letting you that pressure, letting some water out until the bowl is refilled.