The chemistry of the strongly electron donating tetrathiafulvalene (TTF) molecule is exceptionally well known, but detailed knowledge of the chemistry of its technologically important one (TTF⁺˙) and two (TTF²⁺) electron oxidised redox partners is limited. In this paper, the different pathways that apply to the reaction of TTF, TTF⁺˙ and TTF²⁺ with water have been identified in the absence and presence of light. On the basis of data obtained by transient and steady state voltammetric methods in CH₃CN (0.1 M Bu₄NPF₆) containing 10% (v/v) H₂O, TTF is shown to participate in an acid base equilibrium reaction with HTTF⁺, with H₂O acting as the proton donor. In contrast, TTF⁺˙ generated by one electron bulk oxidative electrolysis of TTF remains unprotonated and fully stable in the presence of 10% H₂O in the dark. However, when this cation radical is exposed to white or blue (λ = 425 nm) light, TTF⁺˙ is photoreduced to TTF, with oxidation of water to give oxygen (detected by a Clark electrode) and protons that react with TTF to give HTTF⁺ as the counter reaction. Again emphasising important reaction pathway differences associated with each redox level, TTF²⁺ generated by bulk two electron oxidative electrolysis of TTF reacts rapidly with water, even in the dark, to give TTF⁺˙, protons, HTTF⁺ and oxygen as the products.