When we say water is essential for our life we mean clean water. It is true that man cannot live without water. But it is also true that water is the carrier of germs of many fatal diseases. Clean water saves our life and on the other hand, unclean water kills us. We drink water and use water in various ways. About eighty percent of our body is water. From this, we can easily imagine the importance of water. When we say clean water we mean that the water is good for our health. Plants and bacteria are some sorts of life and they can live with unclean or impure water. But if the water is polluted by some harmful chemicals no life can grow in it. Completely clean water is rarely found in nature. The rainwater and distilled water are completely clean. Some sorts of bacteria and minerals are mixed in water. And all bacteria are not harmful to us. There are some bacteria and minerals which are good for our health while most other are injurious. So while drinking water we should be careful about its purity. We can clean water in various ways. But the best way is to boil it for half an hour.