Design and build a device that can clean a dirty water sample using materials around your home. You’ll follow the same design process used by NASA engineers and scientists when they developed the water filtration system for the International Space Station orbiting Earth. To do so, you’ll use an iterative process, meaning you’ll test multiple designs, look at how your materials get you closer to your goal, and record your findings to build the best filter possible.

Important safety note! This activity is not designed to make drinkable water. No matter how “clean” your filtered water looks, you should never drink it because it still may contain pollutants you can’t see.

› Educators, explore how to turn this into a standards-aligned lesson for students

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See below for materials and step-by-step instructions. For more video tutorials and activities like this one, visit Learning Space.

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In this episode of Learning Space, you'll use materials from around your home to build a device that can clean a dirty water sample like the water filtration system on the International Space Station. | Watch on YouTube

Photo of the materials for the water filtration activity


Photo of a person spooning dirt into a jar of water

1. Create a dirty water sample

Start by preparing the water you’re going to filter. This can be done in many ways that change how difficult it is to filter the water. For example, mix some soil or dirt with tap water for an easier challenge. Try also adding food coloring or vinegar for a bigger challenge.

This dirty water sample will simulate wastewater. On the space station, this wastewater is made up of everything from the fuel that powers the station to astronauts’ sweat.

Photo collage showing the steps to make the water filter cartridge

2. Build your filter cartridge

Until a few years ago, water needed to sent up to the space station in large containers the size of duffel bags. But in 2010, a filtration system was installed that made it so that water could be cleaned and reused onboard the space station.

To build your own filtration system, you’ll need a filter cartridge. Start by carefully cutting your water bottle in half, across the width of the bottle. Remove the cap from the bottle. Put gauze or cheesecloth over the opening and secure it with a rubber band. Turn the top half of the bottle upside down (so the part with the cheesecloth or gauze is facing down) and place it into the bottom half of the bottle.

If you want to fit more materials in your filter, you can use two bottles. You can also use larger bottles or try other containers. Note: Clear containers will help you see the filtration as it takes place.

Photo of a person pouring grains into their DIY water filter

3. Design your filter

The filtration system on the space station has several stages that first filter out larger debris, then smaller impurities and even bacteria. You may want to use similar layers in your filter.

Mix or layer the filter materials you’ve collected in the top of your filter cartridge. Write down what filtration materials you use and how much.

Animated image of a person pouring their simulated wastewater into their DIY water filter

4. Test and evaluate the results

Pour your simulated wastewater into your filter and observe the water that comes out at the bottom of the filter. How effective was your filter at cleaning the water? Write down what you notice. How long did it take to filter the water? What worked well? What could be improved?

Important safety note! No matter how “clean” your filtered water looks, you should never drink it because it still may contain pollutants you can’t see.

Photo of a person writing down a plan for a second version of their DIY water filter

5. Revise and try, try again!

Revise your filter based on what you saw during the last step. Then, test it again. Consider using the same amount of wastewater for each test so you can better evaluate how well your filter is working not just in terms of the color of your filtered water, but how much you’re able to clean, or reclaim.

The filtration system on the space station reclaims 93% of the water onboard. Every drop counts!

As you revise, you’ll find that some filter materials work better than others – not just at filtering out solids like dirt, but also in removing colors. Keep redesigning and testing your filter. Your goal is to produce as much clean water as possible during a single time through the filter.

Remember: Do not drink the dirty or filtered water!