The main objective of this research was to study the behavior of large-diameter tank foundations during hydrostatic testing, by interpreting the settlements measured in the field (Surface Foundation Case) and the perimeter settlements calculated in a three-dimensional numerical simulation using the finite element method (Piled Radier Case), in accordance with the national and international standards that regulate the evaluation of these structures. The methodology consisted of interpreting the settlements, both measured and calculated, based on what is described in standard N-270 (2020) and complemented with standard API-653 (2018). The results of the analysis showed that, by properly treating the settlements observed at the tank control points, it is possible not only to verify the compliance of the settlements allowed by the N-270 (2020) standard, but also to understand the mechanical behavior of the materials that make up the tanks in accordance with the API-653 (2018) standard by analyzing the out-of-plane settlements using the settlement criteria consolidated in the standard. Among the conclusions of this study are significant results that highlight the crucial need to consider not only the settlements of tank foundations, but also the detailed assessment of the components that make up the tanks as a fundamental part of the analysis.