2-[3-(1H-Benzimidazol-2-yl)prop­yl]-1H-benzimidazol-3-ium 3,5-dicarb­oxy­benzoate–benzene-1,3,5-tricarb­oxy­lic acid–water (1/1/1)

The title compound, C(17)H(17)N(4) (+)·C(9)H(5)O(6) (−)·C(9)H(6)O(6)·H(2)O, contains a protonated 2,2′-(1,3-propanedi­yl)bis­(1H-benzimidazole) cation, a deprotonated benzene-1,3,5-tricarb­oxy­lic acid anion, a neutral benzene-1,3,5-tricarb­oxy­lic acid mol­ecule and a water mol­ecule, which are linked together through N—H⋯O, O—H⋯O and weak C—H⋯O hydrogen bonds into almost double sheets parallel to (4[Image: see text] [Image: see text]). These hydrogen-bonded sheets are packed in the crystal with the formation of centrosymmetric voids of 25.5 Å(3), which are filled by the water mol­ecules.