Sand Filter Science Experiment
We had such fun making our sediment jar, we had to continue our outdoor, water-themed science. This time, we decided to try making a sand filter. The sand filter science experiment shows kids how particle filters work, how water naturally settles and cleans itself, and how they might be able to survive if they are ever in a situation where they cannot get to clean water. My kids had a blast making this sand filter because it combined their two favorite things: water and dirt.
Sand Filter Science Experiment for Kids
Remove dirt from water using other dirt!
You’ll need just a few things for this project:
- Medium sized-rocks
- Small rocks
- Coarse sand
- Fine sand
- Cotton (you can also use a cotton ball)
- Coffee filter
- Twine
- Duct tape
- Large mason jar
- Plastic water bottle (we used a smart water bottle)
- Dirty water
- Scissors
Cup off the bottom of the bottle with scissors. You can make the filter as tall or short as you like, but the taller the filter, the more effective it will be at removing particles from the water.
Tie a coffee filter onto the top of the bottle with string. Place the bottle upside down in the mason jar and tape in place (you might not have to tape it).
Stuff a piece of cotton into the top of the bottle. Layer the other materials as follows:
- Fine sand
- Coarse sand
- Small rocks
- Larger rocks
- Biggest rocks
If you have charcoal, you can also try placing a layer of charcoal between the fine sand and coarse sand. 
Fill a cup with the dirtiest water you can find. Pour it into the filter.
Watch as the filter works its magic and cleans the water!
Run the water through the filter several times to make it even cleaner.
We don’t recommend trying to drink this water. At this stage, the water is not clean enough to prevent illness.
Sand Filter Science Explained
This filter works like any basic particle filter. The particles in the water are slowly filtered down from biggest to smallest, getting trapped in the layer that they cannot past through. All carbon filter use this method of filtration, and with small enough particles, a sand filter is one of the most effective at removing pathogens and harmful ingredients from water. Our water filter however, was not able to produce water clean enough to drink. But in a survival situation, filtering, and then boiling water in this way is an effective method to get potable water.
