If you’re feeling the heat this week, a DIY sprinkler is a fun way to cool down. All you need is a plastic bottle and some water. This fun backyard science activity is a fantastic demonstration of gravity and air pressure.
How can tightening the lid of a bottle stop water from flowing out of the holes at the bottom? Challenge your mini engineers to find out!
DIY Sprinkler STEM Challenge
You’ll need
Instructions
Why does it work?
When the lid is unscrewed, gravity pulls the water down and out through the holes, reducing the water volume in the bottle. Air rushes in through the loose lid to replace the lost water, which keeps the pressure inside and outside the bottle equal.
When the lid is tightened, air can no longer rush in to replace the water, so any water leaving the bottle reduces the pressure inside, which stops the water escaping. This allows the higher outside pressure to push back against the holes, trapping the water inside.
Extension Challenge
Try one of my other easy air pressure experiments.
Last Updated on June 25, 2026 by Emma Vanstone
