Water Filter

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In this engineering activity, challenge learners to invent a water filter that cleans dirty water. Learners construct a filter device out of a 2-liter bottle and then experiment with different materials like gravel, sand, and cotton balls to see which is the most effective.
Safety note: An adult's help is needed for this activity. [Activity is publicly available through a web crawler capture on Archive.org.]

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$1 - $5 per student

Age Range:
Ages 6 - 11

Resource Types:
Activity, Experiment/Lab Activity


Materials List (per student)

  • 2-liter soda bottle cut in half (by an adult!)
  • napkins
  • gravel
  • sand
  • cotton balls
  • paper cup of dirty water (made with dirt, food coloring, cooking oil, and bits of paper and foam peanuts)


  • Engineering and Technology
    • Engineering
      • Bioengineering/Biomedical Engineering
      • Environmental Engineering
      • Metallurgy and Materials Engineering
    • Technology
      • Agriculture and Biotechnology
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations
      • Gathering Data
      • Formulating Explanations
      • Communicating Results
  • The Nature of Technology
    • The Design Process
      • Invention and Innovation
      • Problem Solving
      • Troubleshooting and Maintenance


To use this activity, learners need to:

  • see
  • touch

Learning styles supported:

  • Uses STEM to solve real-world problems
  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access



  • All rights reserved, WGBH Educational Foundation, 2002

Funding Sources:

  • National Science Foundation, 0229796
  • Corporation for Public Broadcasting
  • The Arthur Vining Davis Foundation
  • PBS