Make a water filter

This fun science experiment turns dirty water clean. (Kind of.)

How do you clean up dirty water?

Not with soap! You need a filter, a device that removes impurities, like dirt, from water. The filter you’ll make here—with the help of an adult—is a super strainer, and it’ll help you clean up your act.


The slower, the better! The longer it takes for water to move through a filter, the cleaner it gets. Water slips easily through the filter materials, but bigger gunk, like dirt, gets trapped. The filter materials usually get finer and finer, so they can catch whatever was missed earlier. Activated charcoal can be near the end of the water’s path, because it uses an electrical charge to grab particles too small for us to see.

Your filtered water is not clean enough to drink. But a plant will love it!

Photographs by Mark Thiessen / NG Staff: Adapted from the Nat Geo Kids book How Things Work, by T.J. Resler