Conclusions on the fulfillment or violation of regulatory requirements ensuring the hygienic safety of the research object of the supervised object are carried out by state sanitary and epidemiological supervision bodies based on the results of laboratory studies of controlled indicators. These are, in particular, conclusions on the safety of drinking water sources for the population. The composition and properties of this water, on the instructions of sanitary and epidemiological supervision bodies and water supply institutions, can be examined equally by accredited laboratories that comply with the accreditation criteria in carrying out their activities. At the same time, unfortunately, it is impossible to guarantee the same results of laboratory testing of controlled microbiological, chemical, and other indicators, due to their variability and measurement errors. As a result, the conclusions about the quality and safety of water obtained by the supervisory authority and the supplier (user), primarily in cases concerning the boundary values of hygiene standards, may differ. For constructive resolution of controversial situations arising in this case, this paper proposes a method of tolerance control, the result of which is a logical judgment on the compliance or non-compliance of controlled quantities with established standards. It is shown how this reduces the risk of erroneous recognition of non-compliance of the composition or properties of water with hygienic requirements and guarantees safe water supply to the population. Authors suggested equations of admission control to assess compliance with the requirements of sanitary, epidemiological, and hygienic safety of controlled facilities. A method convenient for practical use is proposed, and using a specific example of monitoring the water quality of wells in the Talitsky district of the Sverdlovsk region, it is shown how it is possible to establish the water safety of almost half of the initially rejected water sources. The use of tolerance control is recommended if it is necessary to increase the reliability of hygienic conclusions on the safety of a wide range of supervised facilities, for which convenient mathematical expressions are given.