system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do suction cups stick better when wet?
gpt
Suction cups work by removing air from one side of the cup so that the air pressure on the other side of the cup pushes the cup against the wall (or other surface) without anything pushing back. It’s the air pressure in the room pushing against the suction cup that holds it in place.

They lose suction when air has a chance to get back in-between the suction cup and the wall. If the suction cup is dry, it’s easier for air to slowly push its way under the suction cup, and in-between it and the wall, reducing the difference in air pressure and causing it to release its grip. By wetting the suction cup, you’re putting a layer of water between the cup and the wall, which blocks the air from traveling through to the inside of the cup.