In this work is described filtration of fresh water and membrane processes of fresh water conditioning. In this first half of the work emphasis is on the theoretical explanation of water filtration process and membrane filtration. In the part of the work are also explained basic classification, limitations, terms and all factors that have an effect on the fresh water conditioning process. On that way reader become aware of importance of all elements that are needed for getting the final product and that is drinking water, which is the most important substance on the planet earth. The second half of the work is directly related to the first part on that way that is refers itself to the appliance of theoretical knowledge. Through detailed explanation of appliance of all machines that "Hrvatsko primorje - južni ogranak d.o.o. za skupljanje, pročišćavanje i distribuciju vode Senj" uses for conditioning of fresh water from Gusić lake, we are finding out how such machines work, how to keep them in good condition, how long their duration is and at last which filter type provides more efficient and quality results considering in general quality of water which is with development of civilization and development of industry every day becomes more and more important.