The paper presents the results of an experimental study conducted on specific measuring devices - water meters. The aims of the study are to determine the calibration life of the measuring devices as a function of the metrological reliability and to emphasize the parameter deviation as an important research tool for the quality assurance in metrology. The experimental study conducted is aimed at determining the calibration life of water meters of the same type and of precision class B. The research performed on the considered water meters can lead to the conclusion that the appropriate moment for performing the calibration for a specific set of measuring devices can be estimated by using the parameter deviation functions, these being obtained by means of regression analysis.