2-Amino­pyrimidinium dihydrogen phosphate monohydrate

In the title compound, C(4)H(6)N(3) (+)·H(2)O(4)P(−)·H(2)O, the pyrimidin­ium ring is essentially planar, with an r.m.s. deviation of 0.0016 Å. In the structure, pairs of symmetry-related anions are connected into centrosymmetric clusters via strong O—H⋯O hydrogen bonds forming six-membered rings with an R (2) (2)(6) motif. These clusters are inter­connected via water mol­ecules through OW—H⋯O hydrogen bonds, building an infinite layer parallel to the ab plane. Moreover, infinite chains of 2-amino­pyrimidinium cations spread along the a-axis direction. These chains are connected to the inorganic layer through N—H⋯O, C—H⋯O and C—H⋯N hydrogen bonds, which, together with electrostatic and van der Waals inter­actions, contribute to the cohesion and stability of the network in the crystal structure.