Keep the water clean
Build a simple water filter from a plastic bottle, gravel, sand, and activated charcoal to clean cloudy water for observation only.
Step-by-step guide to build a simple water filter
How Can I Save Water? | SciShow Kids
Step 1
Ask an adult for help before you start the project.
Step 2
Wash your hands with soap and water for 20 seconds.
Step 3
With the adult holding the bottle steady cut the bottom off the plastic bottle using scissors or a craft knife.
Step 4
Turn the bottle upside down so the neck points down like a funnel.
Step 5
Push a coffee filter or clean cloth into the bottle neck to cover the opening.
Step 6
Add about 2 centimeters of activated charcoal on top of the filter.
Step 7
Add about 3 to 4 centimeters of sand on top of the charcoal.
Step 8
Add about 2 to 3 centimeters of gravel or pebbles on top of the sand.
Step 9
Place the upside-down bottle funnel over the clear jar or cup so the neck is above the jar.
Step 10
Slowly pour a small cup of the cloudy water into the top gravel layer.
Step 11
Wait until all the water has dripped through into the jar below.
Step 12
If the water is still cloudy repeat Steps 10 and 11 until it looks clearer.
Step 13
Do not taste or drink the filtered water because it is for observation only.
Step 14
Share your finished water filter and what you observed on DIY.org
Final steps
You're almost there! Complete all the steps, bring your creation to life, post it, and conquer the challenge!
Help!?
What can we use instead of activated charcoal or coffee filters if they're hard to find?
Use aquarium activated carbon or crushed, rinsed coconut-activated charcoal instead of the activated charcoal, and substitute a clean cotton cloth or a folded paper towel for the coffee filter in Step 5.
The water is barely dripping through—what should we check or change?
If the water is very slow after you pour in Step 10, check that the filter in Step 5 isn't tightly folded or clogged, replace it with a looser cloth, gently tap the funnel, or reduce the fine sand layer (Step 7) to increase flow.
How can I adapt the steps for younger or older children?
For younger kids have an adult do the cutting in Step 3 and handle sharp tools while the child helps push the cloth in Step 5 and pours in Step 10 under supervision, and for older kids have them measure precise layer depths (2 cm charcoal, 3–4 cm sand, 2–3 cm gravel), run multiple trials, and record observations to share on DIY.org.
How can we extend or personalize the water filter project after finishing the basic steps?
Try a two-stage setup by stacking a second upside-down bottle over the jar to repeat Steps 10–11, compare results with and without the activated charcoal layer, and decorate and label the bottle to personalize your finished filter before sharing it on DIY.org.
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Facts about water filtration and water quality
♻️ Turning a plastic bottle into a filter is a fun upcycling project: it gives trash a brand-new job instead of the trash bin.
💧 A sand-and-gravel filter can make cloudy water look clearer but it won’t remove all germs or chemicals, so don’t drink filtered samples.
🧪 Activated carbon has millions of tiny pores that trap impurities — that’s why it’s used in filters and aquarium tanks.
🪨 Different layers (coarse gravel, sand, activated carbon) each catch different sizes of dirt — it’s like a tiny layered cleaning factory!
🌍 Over 2 billion people worldwide still lack access to safely managed drinking water, so learning about filters helps understand big real-world problems.
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