In the title salt hydrate, C2H10N2 (2+)·C12H10N2O6 (2-)·4H2O, each of the ions is located about a centre of inversion and the asymmetric unit is completed by two water molecules in general positons. In the crystal, the cations, anions and water mol-ecules are connected by O-H⋯O and N-H⋯O hydrogen bonding into a three-dimensional network.