Introduction: Simple Classroom Water Filter

About: University of Oklahoma MLIS Student

This instructable would be a great water filter to design with students especially those in upper elementary or middle school. The simple design of the filter will allow the user to filter out large and small particles as well as clear the water sample to some degree. I made this to show students how the different physical properties of materials can work together to form a function for everyday life. The water filter is made from everyday household items and can be constructed in a short period of time. The instructable also includes directions on how to create a water sample to be filtered. In this instructable, I am going to share my simple water filter plan, as well as some helpful hints to assist in your making process.

**Note: This is for entertainment/educational purposes only. It is not intended to be used as a water filtration system for human consumable water sources.

Step 1: Materials + Tools


  • Drill and 1/4" drill bit
  • Scissors
  • Box Cutter
  • 2 Liter Bottle (2)
  • Measuring Cups
  • Measuring Spoons
  • Funnel
  • Colander
  • Pan 6" X 10"


  • Wash Cloth (1)
  • Cotton Balls (8)
  • Coffee Filters (4)
  • Small Gravel 1/2 cup
  • Fine Sand 2/3 cup
  • Charcoal 2/3 cup
  • Corn Starch 1 Tablespoon
  • Tea Granules 1 Tablespoon
  • Potting Soil 1 cup
  • Water 8 cups

Step 2: Steps to Make the Water Sample

Set a 2-liter bottle into a pan (6" x 10") to catch any spills.

Step 3:

Place a funnel into the top of the 2-liter bottle.

**Note: If the end of the funnel is too narrow, use the box blade or sharp scissors to trim off the bottom of the funnel to make the opening larger.

Step 4:

Measure 1 cup of potting soil.

Step 5:

Pour the potting soil into the funnel.

Step 6:

Measure 1 tablespoon of tea granules.

Step 7:

Add the tea granules to the bottle via the funnel.

Step 8:

Measure 1 tablespoon of cornstarch.

Step 9:

Add the cornstarch to the bottle via the funnel.

Step 10:

Add 8 cups of water to the bottle via the funnel.

Step 11:

Remove the funnel and replace the bottle cap.

Step 12:

Shake the bottled water sample.

Step 13: Steps to Make the Filter

Drill a hole into the 2-litter bottle. (Use the empty bottle)

**Note: Place a block of wood under the bottle cap, so that you do not drill into the tabletop.

Once the hole has been drilled, screw the lid back onto the bottle.

Step 14:

Cut the empty 2-liter bottle into two pieces.

Use the box cutter to start the cut, and then use the scissors to continue cutting the bottle.

The bottom half of the bottle should be cut, so that it is 1" above the half mark. This will cause the bottom part of the bottle to be slightly longer than the top half. You do not want them to be equal in length as the top section will be placed into the bottom section and adequate spacing needs to be available.

Step 15:

Invert the top of the 2-liter bottle and place into the bottom section of the bottle.

The top portion of the bottle should be upside down with the large opening facing up.

Top Section = The Filter

Bottom Section = The Catch Bucket

Step 16:

Place 4 cotton balls into the bottom of the filter.

**Place one of the four cotton balls over the opening of the filter's lid, so that it is in the "neck" of the 2-litter bottle.

Step 17:

Cut a wash cloth in half.

Step 18:

Take one of the wash cloth halves and fold it in half. Then place the folded wash cloth on top of the cotton balls in the filter.

Step 19:

Place 4 cotton balls on top of the folded wash cloth.

Step 20:

Take the remaining half of the original wash cloth and fold it in half. Place the folded wash cloth on top of the cotton balls.

Step 21:

Place 4 coffee filters on top of the wash cloth.

Step 22:

Measure 1/3 cup of fine sand.

Step 23:

Pour 1/3 cup of fine sand into the coffee filters.

Step 24:

Rinse the charcoal in a colander to remove the excess dust.

Step 25:

Measure 1/3 cup of rinsed charcoal.

Step 26:

Pour 1/3 cup of charcoal on top of the sand.

Step 27:

Measure 1/3 cup of fine sand.

Step 28:

Pour 1/3 cup of fine sand on top of the charcoal.

Step 29:

Measure 1/3 cup of charcoal.

Step 30:

Pour 1/3 cup of charcoal on top of the sand.

Step 31:

Rinse the small gravel in a colander with water to remove the excess dust.

Step 32:

Measure 1/2 cup of rinsed small gravel.

Step 33:

Pour 1/2 cup of small gravel on top of the charcoal.

Step 34:

Measure 2 cups of the premixed water sample and pour the water sample on top of the small gravel.

**Pour this gradually so that the water does not run over the top of the coffee filters.

Step 35:

Watch the water filter.

You should notice that there are no foreign particles in the filtered water, and the water has cleared considerably.

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Teachers Contest 2017