The research considers ongoing changes in the current system of legal regulation in the field of water supply and wastewater disposal of multi-apartment buildings (MABs). The authors present results of operational and design standards of water consumption analysis. It is shown that the existing regulatory and technical documents need adjustment in terms of determining the maximum possible consumption of cold and hot water for MABs residential units. The paper also puts forward an algorithm of hydraulic calculation of MABs domestic water supply systems according to the methodology developed in the Academy of Construction and Architecture in Samara State Technical University (ACA SamSTU).