This paper analyzes the usage of grey and rain water in civic amenities. Its main goal is to assess the advantages and disadvantages of the grey and rain water and to dissect the problematic of rain water quality. In order to reach its goal, the current paper will analyze the already applied system of using grey water, specifically in the case of MOSAIC HOUSE in Prague, which was the first in the Czech Republic and second in the world to use grey water for heat purposes. In conclusion, this Bachelor’s paper presents one object of civic amenities, specifically the guesthouse U Cerneho psa in Cesky Krumlov, with the proposal of grey water purifier by ASIO s.r.o. and grey water seepage object from the same company together with a projected bal...