The main scientific goal of the research activity planned as a proposal for the MINIATURA competition is a complex assessment of the quality of collected and stored rainwater, as well as an assessment of the effectiveness of the inline filtration. Inline filter is an element of purification in the rainwater harvesting system, which is designed to collect rainwater from the roof of a single-family building, located in the rural area. It is assumed to perform two series of quality tests of rainwater before and after treatment with the use of the filter, in which the filter filling will be replaced after approx. three months of operation. The filter filling will be made of polypropylene and activated carbon. Water quality tests will cover physico-chemical analyzes and selected analyzes of environmental microbiology. The possibility of leaching substances from the system components into rainwater is also assumed. Therefore, an analysis of metal cations (as a result of leaching from the core of the roofing material) and chromatographic analysis of selected organic substances included in the protective cover of the metal roof tiles, material of gutters and storage tank is planned. The research task will provide information on the variability of the composition of rainwater and the possibility of its secondary pollution as a result of flow through the collection and storage system for economic purposes. Furthermore, the research on the effectiveness of inline filtration will allow to determine the importance of the use of subsequent stages of rainwater treatment. Obtained results will also enable identification of specific application paths, which may become the basis for extended research in future National Science Centre projects.