I made this system a few years ago while camping and it's worked well. I haven't gotten sick after using it (knock wood!) Mainly it's used for shower water or water for boiling into drinking water or other cooking (rice etc ...)
To begin with I made five holes in the bottom of the cup. Somewhat small as I do not want the filter medium to go thru.
Step 1: Begin, Make the Holes
Next, I added the medium, activated charcoal for the final (bottom) layer and washed sand for the upper layer. The sand is mostly to trap material like leaves etc … before the water continues to the activated charcoal.
I used a smaller cup for the sand and a larger cup for the charcoal, so they nest together. After the water drips from the sand, it runs into the charcoal and finally into the final receiving vessel. I’ve used a coffee filter here, but also I’ve done this without the paper coffee filter.
the bubble top came from a whipped cream coffee drink and a 2 liter soda bottle screws into this nicely, creating a reservoir for the dirty water going in .
The water then goes into the cup with the sand, then drips into the charcoal, then drips into your final clean reservoir.
The water can now be boiled if that’s required. I don’t have an inexpensive way to test how much this system removes, but I have used it while camping for cooking, cleaning and with drinking tabs … for drinking. It takes most of the funky smell & taste out.
I’ve also done this with Styrofoam and paper cups, but used plastic here for illustration and durability. Also, I’ve done this with bigger systems, placing this type of filter in the bottom of a five gallon bucket. It’s a cheap way to clean your water and make it more palatable … and re-use some of these drink cups that are EVERYWHERE!
Step 3: I Made This Sound Too Complicated
Sorry about that, I made it more complicated than it is. The cups are just nested 'funnels" with small holes and different filtering media. The top filter is sand, something we have PLENTY of here in AZ. That's used to screen out the big stuff. I put about 2 or 3" in the cup. I nest that cup inside the other cup so that the water dripping from the sand then drips into about 2" of activated charcoal. I get mine at the pet store, but in a pinch I've used charcoal (not ashes! I'm pretty sure there are instructables on making this.) from a fire. To make my coal I put some burning embers under a metal coffee can so they smolder without air and the wood would not completely burn. that isn't "activated" charcoal, but it's a decent filtering medium. It's enough so that the water percolates thru and leaves more of the junk behind. Once that water trickles thru these two medium (sand, then charcoal) the little holes in the bottom of the cup lead to an empty but clean 2 liter soda bottle as my collection reservoir. I still either drink tab or boil the water for more than 21 mins after these steps. I have a healthy sense of self-preservation. I've had bad water in the middle of nowhere and I learned how dangerous that is, please please please take this as intended, as a simple filter, not a purification system.