Let me be real: I’ve taught middle school science in classrooms where chaos was the norm—behavior issues, no designated lab space, and not nearly enough time. The idea of pulling off a lab felt exhausting.
That’s exactly why I started creating science labs that are simple, engaging, and realistic for everyday classrooms.
This STEM challenge asks students to build a water filter using everyday materials,and let me tell you, it’s a total win. It hits on Earth science, engineering, and even touches chemistry and environmental science. Kids get hands-on with gravel, sand, and charcoal, and they absolutely love the chance to design, test, and compete to create the best filtration system.
It’s also one of the easiest labs to manage. You’ll only need common materials (many from your kitchen or Amazon), and it works beautifully as a design lab, demo, or at stations.
If you’re nervous about managing labs, I’ve got your back. I wrote this with you in mind. Keep reading to get all my tips and tricks for making this a smooth, exciting day for you and your students.
Need the student worksheet that goes with this lab? Grab it here!
Here’s what each group will need to build a water filter:
1 empty 2-liter plastic bottle (cut in half)
Coffee filter, paper towel, or cheesecloth
Fine sand
Small pebbles or gravel
Activated charcoal (crushed if not already)
A container or jar to collect filtered water
Dirty water sample (tap water + soil, leaves, food coloring, etc.)
Measuring cup
Optional: rubber bands, funnels, pH test strips, turbidity testers
You can gather most of these from your home, classroom, or a quick Amazon run.
Instead of giving students a strict step-by-step, this lab is more open-ended. That’s what makes it a true STEM challenge. They have to think like engineers and design their own filter using the materials you provide.
Here’s the flow:
Challenge the students: Clean this “dirty” water using only the materials provided.
Explore the materials: Have students examine what’s available and brainstorm what each item might be good for (absorbing odors, catching debris, etc.).
Design & sketch: Students draw their design and decide on their filtration layer order.
Build and test: They assemble their filter using a cut water bottle over a jar, pour the water through, and observe.
Evaluate and improve: They’ll measure clarity, smell, and speed—then reflect and redesign if time allows.
Class competition: Award points for clearest water, most creative design, and best scientific reasoning.
Pre-cut bottles ahead of time to save time and avoid the hassle during class.
Plan to make a large batch of dirty water so that each group starts with the same level of contamination. (Pro tip: This could be a great excuse to clean out your fish tank!)
Consider turning this into a class competition with categories like:
Clarity of the filtered water (use a visual scale or turbidity strips if available)
Filtration speed (how long it takes to filter 100 mL)
Creativity in design or materials
Scientific reasoning and how well students explain their choices
Heads-up: this lab gets messy! Plan to conduct it outdoors, in trays, or on covered surfaces to keep cleanup simple.
This build a water filter STEM challenge is always a hit in my classroom,and not just with students. It’s low-prep, high-impact, and hits a ton of science and engineering standards. Whether you’re deep in your Earth science unit or just need a fun design day, this lab is a perfect fit.
Your students will leave feeling like real engineers, and you’ll walk away thinking: “That actually wasn’t so bad.
If you’re a teacher in the trenches with limited time and resources, I see you. This lab was made for you.
Ready to go? Grab the printable worksheet and teacher guide here.
Happy filtering, science friends!
