Water is a liquid substance. It has three states such as liquid-solid and gas. It is the principal constituent of all living things it is also a key factor in air-conditioning the earth for human existence (অস্তিত্ব) Man uses water for various purposes, such as for drinking, bathing, washing, laundering. Cooking, fishing, swimming etc. Water is also used for agriculture, industrial processes, such as for drinkings, bathing, washing, laundering, cooking, fishing, swimming etc. Water is also used for agriculture, industrial processes, for fire protection and for fish and wild lives propagation The larger the quantity and the better the quality of water the more rapid and extension has been the advance of public health. We get water from oceans, rivers, lakes etc. Polluted water may Contain impurities and pathogens. This polluted water plays an important role in the spread of water-borne (পানিবাহিত) diseases. This is why pure water is needed. Pure water means water safe to drink, pleasant to taste and suitable for domestic uses Rivers and tanks water is polluted and tube-well water is pure.