For trouble-free operation of a centrifugal pump in the facility, the NPSHplant (Net Positive Suction Head available at the plant) must be equal to or greater than the NPSHPump (Net Positive Suction Head required by the pump). The values of NPSH3%=f(Q) are shown in the sales characteristic curves (referred to as ‘characteristic curves’, going forward). This article will examine NPSH3%= f(Q) curves for selected manufacturers of standardized single-stage volute casing pumps with axial inlet. This pump type is significant for this study because of its widespread use in both industrial plants and ships. The presented investigation aims to determine whether the specialized literature and technical documentation provided by manufacturers deliver information about the necessary safety margin on NPSH3% or not.