The hydration of a mildly calcined zeolite Y sample leads to the local destruction of the zeolite lattice. This way, besides the dealumination of the framework, a partial hydrolysis of framework Al-O bonds occurs generating framework connected A-On species. This hydrolysis is evidenced by a peak at 3.1 ppm in the H-1 MAS NMR spectrum, which can only be resolved by applying the H-1 spin-echo MAS NMR technique with different echo delay times. These framework AI-OH sites can host water molecules giving rise to octahedrally coordinated Al species seen in the Al-27 MAS NMR spectrum at 0 ppm. The subsequent adsorption of ammonia on this sample after hydration converts this octahedral coordinated Al back to tetrahedral Al sites. In the Al-27 MAS NMR spectrum these species are now seen by the increased line width of the 60 ppm line.