The present invention relates to a thermal water purification system (10) for producing a distillate liquid from a raw liquid (LP, LB) comprising: - a plurality of distilling units (1 a-1h) which are consecutively flowed through by the raw feed liquid (LP, LB); wherein each distilling unit (1a-1h) comprises one boiling liquid section (2) and one vapor section (3) adjacent thereto; wherein any two consecutive distilling units, respectively an upstream distilling unit (1 a) and a downstream distilling unit (1b), are implemented such that the boiling liquid section (2) of the downstream distilling unit (1b) is separated from the vapor section (3) of the upstream distilling unit (1a) by a liquid-tight and vapor-tight separation plate (6) and from the vapor section (3) of the downstream distilling unit (1b) by a liquid-tight and vapor-permeable membrane (7); - a plurality of heat exchanger tubes (8) adapted to boil the raw feed liquid (LB) inside the boiling liquid sections (2); - a plurality of preheating tubes (9) adapted to preheat the raw feed liquid (LP) before it flows inside the boiling liquid sections (2).