A water tank is used to store water to tide over the daily requirement. In the construction of concrete structures for the storage of water and other liquids, the imperviousness of concrete is most essential.  Design of liquid retaining structure has to be based on the avoidance of cracking in the concrete having regard to its tensile strength.  Cracks can be prevented by avoiding the use of thick timber shuttering which prevents the easy escape of heat of hydration from the concrete mass the risk of cracking can also be minimized by reducing the restraints on free expansion or contraction of the structure.