Bis(2-amino-4-methyl-6-oxo-3,6-di-hydro-pyrimidin-1-ium) sulfate monohydrate.

In the title hydrated mol-ecular salt, 2C5H8N3O(+)·SO4 (2-)·H2O, the components are linked by N-H⋯Os and Ow-H⋯Os (s = sulphate, w = water) hydrogen bonds, generating a layer by a+b+c and 2a-b translations. The cations are arranged nearly in parallel and show displaced π-π stacking centroid-centroid distance = 4.661†(2)†à between adjacent layers.