The title compound, C18H26N4O11, is a proton-transfer compound obtained from pyridine-2,6-dicarboxylic acid and piperazine. The asymmetric unit contains one half-cation, one anion and 1.5 water molecules. There is a centre of inversion at the centre of the cation ring and one water molecule lies on a twofold rotation axis. In the crystal structure, intermolecular O—H O, N—H O and N—H N hydrogen bonds play an important role in the construction of the three-dimensional framework.
