The principal of a cooling tower is to cool the water that has picked up heat generated by Heat exchanger. Scale caused by precipitation of compounds that become insoluble at high temperatures, such as calcium carbonate. Scale interferes with heat transfer and reduces flow. Corrosion is a function of water characteristics and the metals in the system. Corrosion causes premature metal failures: deposits of corrosion products reduce both heat transfer and flow rates. Fouling results from the settling of suspended solids, build up of corrosion products, and growth of microbial masses. Fouling has the same effect on the system as scaling, but fouling also promotes severe corrosion under deposits