Can you turn murky water clear using just charcoal, sand, and gravel? Water treatment plants use these same materials every day. This project lets you build a simple version of their filtration system. You start by pouring dirty water through a kitchen strainer to remove large particles. Then you let the strained water settle in a tube so fine particles sink to the bottom. Finally, you pour the water through a filtering tube packed with layers of charcoal, sand, and gravel. At each stage you observe how the water changes. The layered filter does the heaviest work, trapping tiny particles that the strainer and settling missed.