Before probing electrolyte intrusion, we reproduced by GCMC simulations the isotherm of water intrusion and extrusion for pure water in these zeosils and demonstrate that we reproduce intrusion pressures consistent with the literature. Then, we used the equilibrated zeosils with the water reservoir at high pressure as the initial state to perform Monte Carlo simulations in the osmotic ensemble using our version of the NCMC move. The alchemical work (i.e. the work performed by the system) for inserting a single electrolyte unit is associated to a very low probability of intrusion in silicalite-1 and chabazite while for faujasite, there could be intrusion of electrolyte because of the larger pore allowing a better solvation of the ions. The non-intrusion of electrolytes in the low pore diameter zeosils are consistent with experiments reporting only water as the first intruded species in chabazite and LTA-type zeosils.