The article analyzes the relationship of the system of technical regulation in construction and regulatory relations for the provision of public services. Changes in the current system of legal regulation in the sphere of water supply of apartment buildings are considered. The article shows that the subject of rationing belongs to several areas of regulation, which requires improvement of the methodological basis for the design of in-house systems of hot and cold water supply of an apartment building and the creation of legitimate methodological tools. Recommendations on the formation of methodological procedures, the implementation of which will provide the legal legitimacy of the methods of hydraulic calculation. The method of determining the calculated (limit) costs of cold and hot water in centralized systems of drinking water supply of an apartment building.