Stem: DIY water filtration system inspired by the ISS

 DIY Water Filtration Like the ISS (Minus the Bodily Fluids, You’re Welcome)

Today we’re jumping into a project that is equal parts science, survival skill, and “wow, I cannot believe astronauts actually do this.” We’re talking about cleaning dirty water the way it’s done on the International Space Station — except our version involves zero urine because this is a fun homeschool activity, not a NASA plumbing emergency.

There’s something weirdly satisfying about taking muddy, swampy mystery water and turning it clear again. And knowing astronauts do this while floating around above Earth? Even cooler.

Why This Is Awesome

Astronauts can’t just stroll to a kitchen sink and refill a cup. Water is heavy, expensive to launch, and too precious to waste. So the ISS recycles almost everything:

Sweat

Breath moisture

Condensation

Hand-washing water

And yes… their pee (listen, nobody said space was glamorous)

But after passing through NASA’s extremely advanced system — filters, chemical treatment, distillation, and UV disinfection — the result is very clean water. Genuinely cleaner than some tap water on Earth.

We don’t need all that tech today, but we can recreate the basic idea: filtering gross water into less-gross water.

Supplies

Just a few things from around the house:

Clear plastic bottle (1–2 liters)

Scissors or craft knife

Coffee filter or paper towel

Activated charcoal (fish tanks to the rescue)

Sand

Gravel or small rocks

A cup or bowl

Water mixed with dirt/leaves/grass (embrace the chaos, but not too much)

🧰 Building Your ISS-Inspired Water Filter

1. Prepare the Bottle

Cut the bottom off the bottle and flip it upside down. Boom — DIY funnel.

2. Add Your “Don’t Let the Sand Escape” Layer

Put a coffee filter or paper towel in the neck. This stops your masterpiece from dumping straight out the bottom.

3. Build Your Filter Layers

In this order:

Charcoal – absorbs odors and some chemicals

Sand – traps the finer bits

Gravel – catches the bigger, chunkier chaos

Repeat the layers if your bottle is tall. Go wild (within reason).

4. Make the Dirty Water

Mix dirt, leaves, grass… whatever harmless debris your backyard offers. Science likes drama.

5. Pour and Watch

Slowly pour the dirty water into your creation. The water that comes out will be clearer, cleaner, and significantly less swamp-creature adjacent.

But still not drinkable. Unless you’re role-playing dysentery, which I highly do not recommend.

What’s Going On Here

Each layer has a job:

Gravel grabs big pieces

Sand filters tiny particles

Charcoal helps remove chemicals, smells, and general funk

This is the kid-friendly version of what the ISS does with:

Multi-stage filtration

Chemical reactions

Vacuum distillation

Ion exchange

UV disinfection

All carefully monitored so astronauts don’t accidentally sip something questionable.

Want to Take It Further?

Try experimenting with:

Cotton balls instead of sand

Extra charcoal

Running the same water through multiple times

Different types of “contaminated” water

Talking about drought, water conservation, and real-world filtration

This project opens up tons of great STEM conversations, and kids love watching the water transform.

Final Thoughts

So the next time someone makes a face and says, “Do astronauts really drink THAT?” you can confidently respond:

“Yes, and the final product is cleaner than what’s coming out of your faucet, so calm down.”

This hands-on project is simple, fun, and surprisingly impressive once you see how well the layers work together.