In the title compound, C(11)H(11)NO(4)S·H(2)O, the five-membered thia-zolidine ring is nearly planar, with a maximum deviation of 0.010 (2) Å. The dihedral angle between the thia-zolidine and benzene rings is 49.16 (9)°. Inter-molecular O-H⋯O and N-H⋯O hydrogen bonding is present in the crystal structure.