Give students a fast, hands-on engineering investigation: build a low-cost water filter, change only one design choice at a time (layer order, thickness, sealing, or adding charcoal), and measure which design makes the clearest water the fastest—all while staying under a classroom budget cap.

With tight build rules and simple materials, students plan a fair test, collect two trials, average their data, and create a comparison bar graph.

The teacher guide explains the science—physical filtration (size-based particle trapping) and adsorption by activated charcoal—so you can teach why the best design works, not just do the challenge.

What’s Included

• Teacher Guide: setup, safety, pacing, “materials store” rules, budget sheet, and background science (filtration vs adsorption; flow rate; contact time).
• Student Packet: clear, step-by-step build instructions, controlled-variables checklist, and blank data tables for multiple trials.
• Turbidity Scale (0–5): simple visual rating card for consistency across teams.
• Results & Graphing Pages: summary table and bar-graph template (Average Turbidity or Time by Design Version) with printable graph paper.
• Analysis & Model Answers: three targeted prompts (layer roles, order effects, redesign impact) plus a model CER.
• Rubric: detailed performance rubric aligned to safety, plan/constraints, build quality, measurement & data, optimization, and CER.
• Dirty-Water Recipe (Teacher): easy, repeatable mixture for realistic testing.

Why Teachers Love It

• Truly print-and-go with explicit controls for a fair test
• Real lab skills: variables, iterations, data/averages, graphing, and CER
• Runs in a single period; easy to extend with a second redesign round
• Engaging “budget & store” mechanic that builds design trade-off thinking
• Low-cost, common materials; easy cleanup and high student ownership

➡️ You can get this STEM as well as all my other ones in this series inside my STEM Investigations Growing Bundle. As more labs are added, the price will increase. CLICK HERE to have a look

Best For

Science or STEM; Earth/Environmental science, engineering design, scientific method, data & graphing, stations, enrichment, or sub plans.

Materials Needed

• Cut 2-L bottles/funnels, clear cups/beakers, measuring cup/cylinder; coffee filters; sand (fine); gravel; activated charcoal; cotton/felt; rubber bands; tape; markers/scissors; stopwatches/phones; goggles.
• Dirty-Water Recipe: tap water + a spoon of soil, pinch of glitter/confetti, a few drops of food coloring; optional 3–5 mL vegetable oil.

Estimated Timing

• 1 class period for plan → build → test → iterate (45–60 min).
• Add 10–15 minutes for a second confirmatory trial, CER, or a class share-out.

➡️ You can get this activity inside my STEM Investigations Growing Bundle.

I also have the following STEM Labs in My Store:

• Blow Cup Challenge STEM Lab
• Paper Table STEM Lab
• Pendulum STEM Lab
• Parachute STEM Lab
• Catapult STEM Lab
• Paper Airplane - Angle of Attack STEM Lab
• Bottle Flip STEM Lab
• Paper Helicopter STEM Lab
• Yeast Balloon STEM Lab
• Balloon Lift Design STEM Lab
• Candy Combustion Calorimetry STEM
• Marble Ramp: Height vs Average Speed STEM Lab
• Clean Water Filtration STEM Lab
• Beetle Genetics STEM Lab
• Adaptations by Design - Extreme Environments STEM Lab

NGSS alignment

• MS-ETS1-1/2/3: Define criteria & constraints; evaluate competing solutions; analyze test data to compare and improve designs.
• Science & Engineering Practices: Planning & Carrying Out Investigations; Analyzing & Interpreting Data; Using Mathematics & Computational Thinking; Constructing Explanations; Engaging in Argument from Evidence.