Next to air, water is the necessity of life. We cannot live without it for more than a few days, just as without air we cannot live for more than a few minutes. Therefore, as in the case of the air, nature has provided us with ample amount of water. Man cannot live on barren land where there is no vast tracts of desert land lie utterly uninhabited.
In order to keep healthy, everyone should take 5lbs. of water or other liquid food in 24 hours. Drinking water must be pure. In many places it is difficult to get pure water. There is always risk in drinking well water. The water of shallow wells, and even deep wells with staircase leading down to the water level, should be considered absolutely unfit for drinking purposes. The difficulty is that the appearance and even the taste of water are no guide to its purity. Water which appears perfectly harmless to look at and to taste, can act as poison. The own custom of not drinking from an unknown well or from a stranger's house is worth copying.
In Bengal almost every house has a kachcha tank attached to it. As a rule the water of these is unfit for drinking purpose. River water is also frequently not fit for drinking, particularly where the river is used for navigation or where it passes by a big city and receives its drainage and sewage water.
In spite of what I have said, I know there are millions of people who had to drink what I have described as impure water. But that does not mean that their example is worth of being copied. Nature has provided us with sufficient reserves of vitality. But for that, man would have long ago disappeared from the face of the earth because of his own mistake and transgressions of the rules of health.
Here we are concerned merely with the role of water with regards of health. Whenever we are doubtful about the purity of water, it should be boiled before drinking. In practice it amounts to this that everyone should carry his drinking water with him. Many orthodox Hindus in India do not drink water whilst traveling on account of religious prejudices. Surely, the enlightened can do for the sake of health. What the unenlightened do in the name of religion!