How to make your own water filter science experiment

A water filter science experiment is a fun and educational activity for kids. It’s made mostly from inexpensive household items and will teach your kids how the process of filtration works as they create their very own water filter.

Putting the water filter together is a simple process, easily done on a table in an hour or less. Testing the water filter can take anywhere from an hour to several hours, depending on how fast the water drips.

Here, we’ll show you how to make your own water filter science experiment and learn all about water filtration!


You will need the following materials:

  • Plastic soda or juice bottle
  • Vase or tall drinking glass
  • Gravel or small stones
  • Clean sand
  • Activated charcoal
  • Cotton balls, small cloth or coffee filter
  • Gardening soil
  • Water
  • Scissors or knife


1. Cut off the bottom of the plastic soda or juice bottle using scissors or a knife.
2. Place the bottle upside down into the vase or tall drinking glass.
3. Place one to two inches of cotton balls, or a cloth or a coffee filter inside the bottle as the first layer.
4. Add an inch of activated charcoal as the second layer on top of the cotton layer.
5. Over the charcoal, add about two inches of gravel or small stones as the third layer.
6. Add about three to four inches of clean sand on top of the gravel.
7. Add more gravel to the bottle as the final layer. Leave about half an inch of space from the top of the upside down bottle.
8. Add soil to a glass of water to create muddy water. Alternatively, get creative and add other things like glitter, beads, cooking oil or other materials to make the water dirty.
9. Pour the glass of muddy water on top of the homemade water filter and watch the water drip clean into the glass below.

How to test your water filter science experiment

For this science experiment, it’s best to test the water before and after the filtration.

1. To start, ask your child to make a hypothesis or prediction about the experiment. Encourage them to think creatively!
2. Pour two glasses of water from the kitchen tap. The first glass will serve as the control. The second glass will be dirty.
3. Dirty the second glass of water with materials found around the house. The dirty water can contain things like dirt, potting soil, glitter, dish detergent, kitchen oils, among other materials found around the house.
4. Pour each glass of water through the homemade water filter. Collect the filtered water in a glass. Test both water samples after filtration.

Compare the water samples. Did the homemade water filter clean the dirty water sample? Is the filtered dirty water now the same as the control?

As part of the experiment, you and your child can test different materials to determine which materials produce the cleanest water. Instead of using sand and gravel, try rice and sponges.

You can build several water filters using different materials to determine which materials filter dirty water into clean water.

How the water filter works

The sand and gravel particles act as a sieve, trapping larger material from filtering down with the water as it travels downwards. This kind of filtering occurs in the natural environment as well.

There are many communities that rely on underground aquifers which have accumulated over millions of years as water has filtered through the soil to the bedrock. A classic example of an underground aquifer is Australia’s Great Artesian Basin which covers much of Queensland and South Australia with extensions into the Northern Territory and NSW.

Simple water filter solutions

A homemade water filter is a simple activity that children will love. Not only does the science experiment help children learn about the water cycle, but it’s a hands-on experiment using common materials found around the house or outside that will fascinate them.

At Water Filters Australia, we are all about making filtered water accessible and affordable for Australian households. You can browse our range of water filtration systems and start to experience the benefits of filtered water for your beverages.

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