The asymmetric unit of the title compound, 2C(6)H(9)N(2) (+)·SO(4) (2-)·H(2)O, contains two isomeric protonated amino-methyl-pyridine cations, a sulfate anion and a solvent water mol-ecule. The cations are in the iminium tautomeric form. In the crystal structure, inter-molecular O-H⋯O, N-H⋯O and weak C-H⋯O hydrogen bonds link the components into a three-dimensional network. Additional stabiliza...