In this bachelor thesis is drawn up the proposal of the use of gray water in residential buildings. In the theoretical part of the work is the definition and basic properties of grey water. In the next chapter is an overview of the use of grey water. In the practical part of the work is in the context of the sixth chapter of the draft proposal on the use of gray water in a family house. In the seventh chapter is made on the basis of investment and economic appraisal of the input water savings and other part of the environmental assessment is the use of these systems. The aim of the work is to raise awareness about the possibilities of using grey water in households, making it possible to reduce the consumption of drinking water and reduce the environmental load.