DIY Emergency Prepardness: How to Make a Water Filter: Water is the basic essential to life. People can live up to a week or better without food, but can only live 2-to-3 days without water. Clean water can be hard to find if you get stranded or there is an emergency. If you have to find your own water supply, you must be able to strain out impurities that can make you sick. This article will tell you how to make a water filter.