We apply the new scaling relations and global isomorphism between continuous and discrete systems to find of saturation pressure. On this basis, we obtain the expression for the saturation pressure containing the critical, Z line parameters and two fitting parameters. First we calculate the saturation pressure for a number of model systems and real substances the critical parameters for which are known and verify that the accuracy is acceptable in a wide liquid-gas temperature domain. Then we discuss situation with the saturation pressure for metals (aluminum and iron), the critical parameters for which are unknown in advance and lie in the domain of parameters still inaccessible for experiments.