How to Make Your Own Water Filter Unit

Clean out the plastic bottle with dish detergent and rinse it with fresh water. If the bottle was used previously for water storage, a rinse with fresh water should suffice.

Cut a hole in the top of the bottle large enough to fit your hand in using the utility knife. If you can find a large bottle with a tap and a wide screw lid, you won't need to make a hole.

Spread about 8 inches of cotton wool onto the bottom of the bottle and press it down with your hand to compress it. It will compress further under the weight of the other filtration material and water.

Spread 3 inches of fine-grain sand on top of the cotton wool in an even layer. Top the fine-grain sand with 3 inches of course-grain sand. The different size of filtration materials helps to trap and filter out impurities of various sizes.

Fill the bottle with around 6 to 8 inches of the activated charcoal granules. These granules are readily available at pet stores, aquarium stores and most garden centers.

Top off the charcoal with a layer of fine-grain and course-grain gravel, equally divided in the remaining space to the top of the bottle.

Open the tap of the bottle and run at least 2 gallons of water through the top. This activates the filtration of the water filter unit. Use this water for cleaning or in the garden so it doesn't go to waste. After that, catch the water you put through the filter in a jug for drinking.