The present invention provides an improved water purifier and method. In one possible embodiment, the present invention provides a turbine mounted in or to piping of a pool or spa filtering system. The turbine comprises one or more rotatable elements such as fins, paddles, blades, propellers, or the like which are responsive to water flow through the piping to produce rotation. The rotatable element may comprise magnets which rotate along with the rotatable element to produce a rotating magnetic field. The rotating magnetic field may be utilized for generating electricity utilizing various types of electric power generators. Electricity so produced may be utilized to power a water purification unit such as a chlorine generator, UV generator, or an ozone generator. In one embodiment, the output of the water purification unit is directed into turbulence, such as turbulence produced by the rotatable element, so that the purification efficiency is enhanced.