Water is one of the basic substances needed for life on Earth. As needed for the material and life of all living organisms, it is also needed in industrial processes. There is no branch of industry in which water of certain quality is not needed. Sugar production is an industry that requires large amounts of water. The work presents the process of preparing boiling water in one of the Croatian sugar refinery's power plants. Water used in power plants should be treated before use and all mechanical contaminants, substances that make water hardness, as well as gases that can cause corrosion of boilers, heating elements and pipelines, must be removed. In the work process aw water is analysed as well as water in certain stages of processing, and finally water from the boiler itself. Apart from the analysis of raw water and its processing, the quality of the return condensate, which may contain certain quantities of sugar and whose decomposition products are highly corrosive, are also monitored.