Piperazine-1,4-diium bis­(2-carb­oxy-1H-pyrazole-4-carboxyl­ate) tetra­hydrate

The asymmetric unit of the title compound, C(4)H(12)N(2) (2+)·2C(5)H(3)N(2)O(4) (−)·4H(2)O, comprises one-half of a piperazine-1,4-diium cation, which lies on an inversion centre, a 2-carb­oxy-1H-pyrazole-4-carboxyl­ate anion and two water mol­ecules. An extensive network of inter­molecular O—H⋯O, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds between the cations, anions and water mol­ecules leads to a three-dimensional supra­molecular framework.