We show that some of the thermodynamic regularities following from the van der Waals (VDW) equation, are valid for the real substances and models described by completely different equations of state., These regularities relate to lines of ideal enthalpy, enthalpy minima, and isothermal compressibility maxima. The first one appears to be the straight line on the density-temperature plane, while for the two others there are universal relations, which are the same for various substances and models (argon and Lennard-Jones system as examples). The model systems were studied by Monte Carlo simulations (NVT MC), while experimental data were analyzed for the real substances Our numerical calculations and the analysis of experimental data have shown that for the considered systems these curves are similar to the VDW ones.