The asymmetric unit of the title compound, 2K(+)·2C(6)H(7)N(2)O(2)S(-)·3H(2)O, consists of two potassium cations located on mirror planes, one sulfanilamidate anion in a general position and one and a half mol-ecules of water, one of which is also located on a mirror plane. One potassium cation is seven-coordinated by six sulfonyl O atoms and one water mol-ecule, whereas the other is surrounded by six water O atoms and two sulfonyl O atoms. In the crystal structure, the components are connected into polymeric sheets in the bc plane. The two-dimensional structure is consolidated by N-H⋯O, O-H⋯O, O-H⋯N and C-H⋯π inter-actions. The layers are further linked into a three-dimensional network via N-H⋯O, N-H⋯N and O-H⋯N hydrogen bonds.