In the cation of the title salt, C8H13N4 (+)·C4H3O4 (-), the piperazinium ring adopts a slightly distorteded chair conformation. In the crystal, a single strong O-H⋯O inter-molecular hydrogen bond links the anions, forming chains along the c-axis direction. The chains of anions are linked by the cations, via N-H⋯O hydrogen bonds, forming sheets parallel to (100). These layers are linked by weak C-H⋯O hydrogen bonds, forming a three-dimensional structure. In addition, there are weak π-π inter-actions [centroid-centroid distance = 3.820 (9) Å] present involving inversion-related pyrimidine rings.