The anion of the title salt, 2C(4)H(12)N(+)·S(2)O(3) (2-)·4H(2)O, possesses approximate C(3v) symmetry. The water mol-ecules themselves engage in hydrogen bonding, forming a ribbon running along the a axis; adjacent chains are linked to the thio-sulfate anions by hydrogen bonds, forming a three-dimensional network. The cavities in the network are occupied by the tetra-methyl-ammonium counter ions.