An apparatus for purifying liquid comprises a substantially tubular irradiation chamber (100) and a plurality of UV-LEDs (110) projecting ultraviolet radiation into it so as to irradiate the flow (106) of liquid being passed through it, where each of the UV-LEDs (110) is disposed upon the irradiation chamber (100) so that it is illuminated by at least one other of the plurality of UV-LEDs (110).
