The image text reads, "How to create a DIY water filter." The image shows a water filter created from a 2 liter plastic bottle next to a sample of polluted water.

How to Create a Water Filter STEM Project

By Trilby Hillenbrand

DIY water filters are an impactful STEM project. The learning experience can inspire and empower students to become environmentally conscious problem-solvers and equip them with the skills and knowledge to tackle global challenges related to water quality and sustainability. The benefits are many but you may be wondering, “How exactly do I create a water filter?” This step-by-step guide will help you plan an engaging STEM project with real-world applications.

Disclosure: This post contains affiliate links. This means I get a commission if you decide to purchase through my links, at no cost to you.

Yes, please!
The image text reads "Water Filter STEM Challenge." It shows a sample of polluted water and a DIY water filter created from a 2 liter plastic bottle.

Why water filters?

Water is critical to human survival, but clean water is a limited resource. One in 10 people on Earth doesn’t have access to clean water (Reid, 2024). Affordable home water filters would increase access to clean water around the world. Students will take on the role of environmental engineers as they design and build water filters from household materials.

Understanding water treatment methods

There are various methods for purifying polluted water. These methods are often combined to achieve better results. 

  • Coagulation involves adding chemicals that will cause solids dissolved in water to form clumps that will settle out of the water sample.
  • Sedimentation is when solids are allowed to settle to the bottom of the water sample. 
  • Filtration happens when water moves through filters with different pore sizes and different materials designed to remove various dissolved particles and germs. 
  • Disinfection kills any remaining parasites, bacteria, or viruses through the use of heat, chemicals, or UV light.

DIY water filters typically focus on filtration using various household materials to filter out visible particles from polluted water.

This image shows a sample of polluted water, a sample of clean tap water, and 7 DIY water filters created from 20 oz plastic bottles.

Step-by-Step Guide to a Water Filter STEM Challenge

Gather materials

  • An empty 20 oz, 1 L or 2 L plastic bottle
  • Materials to use for filtration, such as sand, gravel, coffee filters, cloth, paper towels, activated charcoal*, and cotton balls
  • A visibly polluted water sample**
  • Scissors
  • Optional: Water quality testing tools

*Activated charcoal will significantly improve the appearance and smell of the water. If possible, I highly recommend giving your students access to this material.

** You can collect a polluted water sample, or create your own with tap water, dirt, oil, glitter, or other materials you have on hand.

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Introduce the project

Share some statistics with your students to help them understand the importance of clean water and the related challenges people face worldwide. Introduce students to the goal of creating an affordable water filter made from household materials that will visibly improve the quality of a polluted water sample. For an extra layer of excitement and engagement, show them the polluted water sample they’ll be working with. Give students the project criteria and constraints, including their available materials and time limit. Describe how their final designs will be tested and evaluated. You may also want to provide them with a sample frame for their filter, as shown in the diagram below.

Brainstorm Water Filter Designs

Give students time to research water filtration methods. Then have them consider the available materials and brainstorm ideas for their water filter design. Review and approve student designs before students begin building.

This image text reads, "How to Create a DIY Water Filter." The image shows a plastic water bottle cut in half with the top half inverted and placed inside the bottom half.

Create the Water Filters

Students should start by cutting their water bottle to create the filter on top and the clean water receptacle at the bottom of the bottle. The top of the water bottle should be inverted and placed inside the bottom of the bottle. Then students can layer the materials they chose to create a water filter inside the top half of the bottle.

Test and Evaluate the DIY Water Filters

Students should slowly add polluted water to their filters and observe as the water moves through their filter design and collects at the bottom of the water bottle. They can compare the appearance of their filtered water to a sample of unfiltered water. They could also perform more advanced testing using water quality testing kits or electronic devices to get quantitative data about the performance of their water filter.


After testing their initial designs, challenge students to improve the performance of their water filters. Students can do more research, observe their classmates’ designs, and reimagine their DIY water filters. 

This image text reads, "Water Filter STEM Challenge: Print and Digital." It shows a worksheet titled "Water Filter STEM Challenge" and a DIY water filter created from a plastic bottle.

Looking for more support with your DIY water filter project?

Check out this done-for-you water filter STEM challenge that is sure to excite and inspire your middle school students! 

First, students will learn about clean water as a limited resource. Then they’ll research methods for treating and filtering polluted water. Next, they will use the engineering design process to design, build, and test DIY water filters. With detailed teacher notes, engaging student worksheets, a lesson slideshow, embedded background research, a grading rubric, and end-of-project certificates included, you only need to make copies and grab the materials from your cabinets to get started.

Grab this resource today so you can take a break from planning and know your students will still be learning and having fun!

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Works Cited

Centers for Disease Control and Prevention. (2022). Water Treatment. Retrieved April 7, 2024 from

Reid, K. (2024). Global water crisis: Facts, FAQs, and how to help. World Vision. Retrieved January 22, 2024 from,hours%20carrying%20water%20every%20day

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