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Science Rocks!

Water Filter


your results

Sent in by:
Jaban of Greene, ME and Cara of Maple Plain, MN

Hydro-neers wanted. Invent a filter to clean dirty water.

Materials Needed

  • 2-liter soda bottle cut in half (by an adult)
  • napkins or paper towels
  • gravel, sand and cotton balls for your filter
  • dirty water, you can make it by adding cooking oil, food coloring, pieces of paper, and tiny pieces of Styrofoam to water



  1. Put the top half of the soda bottle upside-down (like a funnel) inside the bottom half. The top half will be where you build your filter; the bottom half will hold the filtered water.
  2. Layer the filter materials inside the top half of the bottle. Think about what each material might remove from the dirty water and in what order you should layer the materials. For an added challenge, use only two of materials to build your filter.
  3. Pour the dirty water through the filter. What does the filtered water look like?
  4. Take the filter apart and look at the different layers. Can you tell what each material removed from the water?
  5. Wipe the bottle clean and try again. Try putting materials in different layers or using different amounts of materials.

Now it's time to experiment. Think of a question you want answered. Like, are there better materials for cleaning water? Be sure to predict what you think is going to happen. Then, test it out using different materials and send your reports in to our special feedback area. Every week, we'll publish a whole bunch.

Some of your Results

Marr, age 12 of FL wrote:
it was awsem I did evrithing okay and the water came aut crystal clear

Wyees, Xavier & Kendall of Chicago wrote:
It came out alright we had 2 use different materials though paper towels, cotton balls, gravel and mesh wire it came out fine. We didi this 4 our science project so i mean if u want good quality u need 2 have good materials

Loren of Kenner, LA wrote:
well I put the gravel first then sand the cotton balls to take away the food coloring... I came out perfect im a junior in high school and this worked out so well thanx zoom!

Leroy, age 13 of Jacksonville, FL wrote:
i mxed oil in some water and poored sand in the bottle and then I shook it up the I poored in the my filter and it came out crystal clear

Phoebe, age 9 of Bristel wrote:
the water was very very clean at the end of the experiment

Henry, age 9 of Coquitlam, BC wrote:
When I poured the water through the filter, it came out crystal clear! I used cotton at the top, gravel at the middle, sand at the bottom, and paper towels at the bottom. Cool!

Samantha, age 11 of ME wrote:
I used rocks, sand, cloth, sponges, gauses, but the material that worked the best was the sponges, the cloth and the gauses.

Stacy, age 16 of Baltimore, MD wrote:
When I first did it the water was cstilla little dirty then I tried the next trail the was was refreshing and clean

Kd, age 11 of WI wrote:
it worked ok. I need better materials though. if I try it in summer it would work good because I could get sand

Molly, age 15 of San Diego, CA wrote:
it came out totaly clear!!! it was amazing!!! what happened when you guys tried it?

Annie, age 8 of Bend, OR wrote:
it was ok... I didn't come out all clear but it was pretty clear.

Kaomii of Blandford Forum, UK wrote:
I printed the instructions for school and we did it as a class project and everyones was crystal clear! They were so amazed!!!

Keyshia, age 4 of Hawaii wrote:
well first it was dirty then when the tryed it again the h2o was clear but still a little dirty

Amal, age 12 of Toronto, ON wrote:
I tried the experiment and it went great! I didn't finish but I was just wondering what you can use to separate the food coloring and salt? Please can you give me an answer?!

Cooper, age 12 of Sunderland, MA wrote:
it worked fine at home. the water was clear. it did not woke as nice st school.

A.J., age 12 of Toronto, ON wrote:
it didn;t work, the water stayed th same!!!

Jessica, age 11 of Naples, FL wrote:
When I first did the expirement it worked out not very good but the second time was perfect so if you are doing it for a science fair I suggest keeping two containers of dirty water instead of one!

Claudia, age 12 wrote:
The water was clean

Jacod, age 11 of Naples, FL wrote:
The Expirement was for my science fair expirement and it turned out real well and very nicely. The finishing water was much more clear and clean than before I put it in the filter!

Sisqo of Philadelphia, PA wrote:
It was so awesome when I tried. It came out so clear and clean. Thank you so much ZOOM you guys are the best.

Brayin, age 4 of Indianapolis, IN wrote:
Here is what we used cotton, rocks, a little sand, more cotton then add drity water. Guess what the experiment worked. Then the water was filtered out.

Garrett wrote:
It keep the particles from geting to the water.

Tien, age 11 of Perth wrote:
The water came out clean. I think my teacher got this idea from you because we did this at school. The same ingredients as well.

Dhruv, age 16 of Ahmedabad wrote:
When I did it I got the water which was realy very clean.

Gretchen, age 11 of Eugene, OR wrote:
I tryed evaporation because, when water evaporates it cleans the water and leaves behind any dirt. I put the dirty water in a boal and coverd it with cloth so when the cloth was wet, I sqeezed the clean water out into a boal.

Shymarebecca, age 12 of Bangalore wrote:
It worked the water came out crystal clear the first time we tried. Super cool!. We put tissue, stones and pebbles, cotton, sand(washed) and sponge.

Parnit, age 8 of Brampton wrote:
The first time I tried it the water came out dirty, but the second time I tried it, it worked.

Diana, age 13 of Chicago, IL wrote:
This really works! The first time I tried it the water came out blue since I used blue food coloring. I put a paper towel on the bottom of the container so nothing would seep through at the end. The color went away. The water was crystal clear!

Susan, age 11 of Singapore wrote:
The water came out like, crystal clear even though I used muddy water!! It is unbelievable!

Cristin, age 13 of Fredericksted wrote:
The water turned very clean when I tried out this project with the filter. I wanted to see how clean the water would have gotten. By time I put the sand gravel and everything and made my dirty water. I poured the dirty water into the filter. Waiting to see my results the water was much more cleaner and clearer than when I put it in there.

Lisa, age 15 of North Bay, ON wrote:
When I did the water filter the first time it did not work. But I tired once more and the water came out clean.

Elizabeth, age 13 of Charlotte, NC wrote:
I used part of a spounge, dry wall sand paper, cotton balls, paper towels, but the item that worked the best in my filter was copy / printer paper. You should really try it!!! It works!!!

not yet implemented