Earth Science Week Classroom Activities

Design and Build a Water Filtration System

Activity Source:

United States Geological Survey. Adapted with permission.

Access to clean drinking water is necessary for human health. But how do we get clean water? What happens to our water between its source and our faucet? What parts of the environment might act as a water filter? How can humans filter water to make it cleaner? This activity will allow you to investigate the ability of materials to filter particles from water.


  • 2 L plastic bottle
  • Scissors
  • Water with coffee grounds or soil (unfiltered water)
  • Large cup
  • Natural filter materials: soil, gravel, sand, dried grass, or others
  • Other filter materials.
  • ​Consider:
    • Paper products
    • Pet care materials
    • Hardware store ​materials
    • Unneeded clothing or packaging materials

If you have an idea, test it out!


  1. Carefully cut the bottom off the 2 L bottle and remove the cap. Place the bottle upside down into the mouth of a large cup.

  2. Layer filter materials inside the overturned bottle.

  3. Run tap water through the filter a few times to wash away any particles on the filter material. Empty the cup after each rinse.

  4. Evaluate your unfiltered water. What does it look like? Is there a color? Do you see anything in the water? Does it have a smell? What materials might be easy to filter out of water? What might be difficult to filter out?

  5. How might each material in your filter help clean the unfiltered water?

  6. Pour your unfiltered water into the overturned bottle with the filter material. It may take some time for water to move through the filter material.

  7. Make observations of the filtered water collected in the cup.

Safety Note:Do not consume the water filtered during this experiment.__

  1. Make changes or build a new filter by repeating steps 2–6 using different materials.

  2. Communicate your findings to others with a talk, poster, or short report.


  1. How does each sample of filtered water compare to the unfiltered water? Why do you think that is the case?

  2. How does each filtered sample compare to each other? Which filter was most effective? Overall, which worked better as a filter- natural or manmade materials? Describe how you know.

  3. Choose a filter that you consider to be ineffective. How could the filter be changed to improve its function? If possible, test your suggestions.

  4. Research where your drinking water comes from and how it is filtered before it gets to your faucet. If you filter your water at home, research what types of contaminants your filter can remove from drinking water.


  1. Even if run through a filter, the water sample you used is likely not safe to drink because it has not been purified. What else may be in the water that you cannot see? Research ways that contaminants that are too small to see can be removed from water.
  2. Quantitatively evaluate your water by measuring the pH or electrical conductivity (EC). Cleaner water will have a pH near 7.0 (the pH of pure water) and a lower EC (a poorer conductor).


USGS Drinking Water and Source Water Resources


SEP :Planning and Carrying Out Investigations

DCI :ESS3.A: Natural Resources

CCC :Cause and Effect


3 : Good Health and Well-Being

6 : Clean Water and Sanitation