Adsorption isotherms of pure water in the zeolites were computed with GCMC simulations using the RASPA simulation package. We screened several values of the chemical potential of the (fictitious) bulk fluid reservoir to compute the number of adsorbed water molecules, by using the relationship between chemical potential of water and hydrostatic pressure µ water (P ). In order to explore the phase space, translation, rotation and swap moves were applied to water molecules, in a ratio of 1:1:2 respectively. Each simulation consists of 4 × 10 5 equilibration cycles followed by 2 × 10 5 production cycles where the average quantities were calculated. In addition, we characterized the thermodynamics of water intrusion by showing the evolution of potential energy per water molecule as a function of intrusion pressure.