Understanding of membrane fouling mechanisms enabled us to exclude certain pre-treatment steps when applying RO techniques to treat well and surface water. This approach is based on result of a long-term course of research devoted to determination of membrane scaling/fouling propensities for different feedwater conditions and to predict membrane performance due to fouling. The results of scaling, organic, colloidal and biofouling investigations are presented. The membrane fouling studies revealed strong "governing" foulant among other water species that influence membrane behaviour. Basing on the fouling build-up prognosis, adequate cleaning techniques are scheduled to remove deposits properly and to ensure desired performance throughout long membrane life. In the distribution of membrane systems Waterlab follows its concept, based on simplified built-in pre-treatment. This provides considerable cost savings that stem from reduction of capital and pre-treatment costs. High product water quality, low pricing and simple maintenance enables Waterlab to overcome customer doubts about RO reliability.