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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

Lidia, age 13 of Deer Park, NY wrote:
it was so fun doing this type of filter im going to take this to my social studies teacher because she gave us a week to do this and it came out well

Ashleyy, age 14 of Toronto, NY wrote:
When we did this experiment it exploded.. well more like fell over and got dirt and water everywhere. it was starting to work ar first but it just tipped over: we still got a desent mark!

Tori, age 11 of Chicago, IL wrote:
The water truned clean and it was amazing.

Andrey, age 13 of Charlotte, NC wrote:
The water was amazingly clear!!! At first I doubted it would work but it worked really well!!!

Nickii, age 9 of New York wrote:
it did not come out right.

Lydia, age 10 of Stone Mountain, GA wrote:
it worked I did it for my science fair project and it worked it was clear and drinkable

Bobby Ray of Montgomery, AL wrote:
I performed that experiment but it wasent drinkin water or nothin.. still goo-oo-ood though!

Jhon, age 9 of OH wrote:
I do this for my school science fair is great it easy fast and fun. At first we had a lot of problems but then it was so easy

Jake & Aidan of Montclair, NJ wrote:
The dirt came out but the oil didn't. Perhaps it was because we didn't have gravel or sand. We used rocks and marbles. Also we didn't have regular cotton balls, so we used cotton pads.

Saad, age 11 of Al-Khor wrote:
COOL!!! I did it for my science fair project. I layered them in different order but the best was sand on top of gravel, and cotton at last. Thank you Ms. C.

Dominik, age 13 of San Diego, CA wrote:
I loved this! I had to do it for my science project but it was more fun than work! I layerd the elements in different orders but found the most successfull was gravel on top, sand, then cotton on bottom! Great job zoom!

Richard of Escondido, CA wrote:
activated charcoal is cheap. use that to make a real water filter using coffee filters or tea bags. pour tap water through that and test it using OTO, a pool/chlorine reagent.

Aasha, age 12 of Peachtree City, GA wrote:
Me and my best friend did a pH project, so we decided to put the creek water through the filter. we put it through the filter every day for 5 days. When that 5th day came the pH was 7. 2(which is neutral) this is a great project to do even if you are in middle school(i am in 7th grade)!!! I had soooooo much FUN!!!

Talia, age 10 of Durban wrote:
Me and my friend Hannahj had to do this for a school thing. It turned out pretty well expect that it was a little dirty but the second time we did it. it turned out a little clearner!

Hannah, age 11 of Wellington, NZ wrote:
I had to do this for science homework and it was great! The water came out a little cloudy but it worked! I used sand, pea gravel, pebbles and cotton balls on the bottom. Works well!

Liliana, age 13 of Canada wrote:
I Did It For My Science Fair. The Water Came SOoo Clear The Techears Drinked And They Love It.. It Was Really Great. I Love It.

Matthew, age 12 wrote:
When the bottom of the bottle filled with water, the clay I put at the bottom made the water white and foggy.

Mikayla, age 12 wrote:
For my experiment, I used a piece of screen from a window, and doubled it up. It worked, but it didn't catch all of the dirt. It caught most of the dirt, but not the smaller pieces of dirt. I think that when and if I ever do this experiment again, I will use something with smaller holes in it like a piece of fabric or layler the screen a few more times.

Ashley, age 12 wrote:
When I did this project, I used uncooked spagetti, cotton pads, sponges, a strainer, and beads. When I did this, it worked great and I got second place in my class. the sifter was on top and got the big chunks out. The spagetti got the rest out. I was suprised but the spagetti worked the best. I enjoyed this experiment.

Dylawnie, age 12 wrote:
Mine came out the best in my class. I put two layers of fabric (handkerchief), put cotton inside the nozzle, and covered the cover with elctrical tape.

Nick, age 13 wrote:
i used three traditional coffee filters to filter my dirty water. it worked out great. I was third best in my class.

Paradyse, age 10 of Springfield, MA wrote:
it worcked better than A real one so I use it all the time even my family loves it.

Meli, age 13 of MA wrote:
i did it as a lab in school and it was awesome. we mixed salt with sand then we mixed that with water. as a filter we used a coffe filter. the water we got out, we heated. the water evaporated and the salt stayed behind.

Treanna, age 12 of AZ wrote:
the first time it came out kinda yellowish then I tried again with only the cotton balls and gravel and it came out clear! thank you sooooo much for making me have the best science fair ever!!!

May, age 13 of London, UK wrote:
when I tryed this I found out that filter paper was the best

Joe, age 12 of Chicago, IL wrote:
it came out awsom- the thing is we aded activated carbon. that got the bacteria out.

Wyatt, age 12 of IL wrote:
I tried to do it with only the paper towels and gravel. It actually worked pretty well, though a bit of food coloring still leaked trough.

Latasha, age 9 of Baton Rouge, LA wrote:
I made a water filter and mine came out great. my drity water was mixed with dirt, I put a paer towel in then I pour the water in it and it started to filter. I was happy my water came out very very clear.

Ennis, age 7 of Milton, NZ wrote:
it came out dirty!!!

Zack, age 15 of O'Fallon, IL wrote:
it didnt help.

Haadiya, age 11 of Botswana wrote:
i did not have much hope untill I tried it and it was very clear the water.

Bridget, age 13 of NH wrote:
it worked well. make sure the gravel is clean and I used pond water instead of trying to make the water dirty. great for science experiments!

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