Merus is used very successfully in certain cooling towers. Greater binding of the calcium carbonate to the water causes a substantial drop in scaling up of the cooling tower. This is important, above all, if baffle plates or fans are used. On one version of cooling towers, the effect of Merus is greatly reduced: on cooling towers on which the water is sprayed by means of spray balls. On these models, it is frequently the case that, owing to design reasons, no flowing water film occurs on the walls of the cooling tower. There are many small droplets which evaporate directly. This results in a great deal of scale left behind. If there is no water stream flowing over such deposits, this scale may harden as if no treatment unit were fitted. The only way to establish this is by testing. Cooling towers scale up if untreated water is used.