There are plenty of ways to make a water filter
The first thing to do is to take the 2-liter soda bottle and cut it in half. Place the top half of the doa bottle upside down onto the bottom half of the soda bottle. This will create a funnel like posture. Now, you will want to begin to build the filter of your choice in the top half of the soda bottle. The bottom half is simply there to catch all the the newly filtered water. Take the cotton balls and place them in the 2 liter bottle for the first layer of your filter. Then put in the sand next. You will want about a 1/2 inch of sand there. Then take the gravel and put a 1/2 inch layer down over the sand. This type of layer will cause all the big things to be caugh first, then filter down to the smaller items, and finally to the last bit of debre or unhealthy items in the water. Pour the water through and see the difference. Enjoy yourself a nice fresh drink that has been filtered for you. If you want to see everything that has been caught, empty the filter appart and look. You will want to change the filter for this water filter at least every other time you use it. It will keep it clean and unclogged. If you do not feel that it is healthy to use cotton balls, you do not have to. All you would need to do is change up the layering of your filter line. You would want to put the gravel in first. About one inch of gravel will work great. You want the gravel in first so that you have the opportunity to keep the sand in its position. Once the gravel is in, place the sand on top of the gravel. You should try to have at least a 1/2 inch of sand, but to make a good filter that will work the best, you will want to have the full inch of sand on top of the gravel. These two items will filter any of the bad contaminants out of the water that you are trying to filter. For information on how to build the perfect water filter go to DIY Water Filter Systems. You will learn how to build a water filter yourself that will remove pathogens and chemicals from your water with the manual that is available from the website. It is simple, quick and as stated, much more effective and much cheaper than the alternatives.