A UV fluid treatment apparatus includes a housing, a treatment chamber defined within the housing, an inlet to and an outlet from the treatment chamber by which fluid is able to flow through the treatment chamber, and a UV lamp within the treatment chamber. A flow sensor located externally of the treatment chamber is operable to sense, and generate a signal indicative of, the flow rate through the treatment chamber. A power supply system and a control system enables and controls operation of the apparatus whereby fluid in, and flowing through, the treatment chamber is disinfected by exposure to UV light generated by the UV lamp.
