1. In an automatic faucet controller comprising an emitter emitting electromagnetic radiation, a detector detecting said electromagnetic radiation and having as an output an electrical signal corresponding to the intensity of said detected radiation, and an electrically operated valve, said controller acting to open said valve when a user's hands proximate said faucet reflect said electromagnetic radiation from said emitter to said detector and thereby provide a said signal exceeding a threshold value, an improvement comprising means for storing a water-offset value equal to said signal corresponding to the intensity of said radiation reflected only from a stream of water from said faucet at a first predetermined time, and means for subtracting said water-offset value from said signal at a second time, subsequent to said first time, when said valve is open, and means for holding said valve open if said signal, less said water-offset value, exceeds said threshold value.