An experimental device for catalytic decomposition of water over zeolites with possibilities of measuring the mass variation of zeolites during UV radiation was built. By means of an electronic microbalance to which an irradiation system of zeolites was added, mass variation of samples and temperature rise of zeolites during irradiation was measured. Microgravimetric measurements of mass variation of zeolites during irradiation were accomplished at the same time with the study of the temperature increase during irradiation. The decrease in weight of zeolites during irradiation, assigned to the elimination of water molecules from zeolite was noticed.