A water purification system having an oil and vapor separation subsystem for removing many heavy duty and toxic contaminants from the water. The subsystem removes volatile vapors from the feed water, heats the feed water, and by imparting a swirling vortex action to the heated water, the oils are separated from the water. The water separated from the oil is pumped by a high pressure pump through a helical coil that is heated to a high temperature by the burner. The high temperature, hot water is then fed to an expansion nozzle in an expansion chamber to flash the hot water into steam. The steam is passed through a condenser which converts the steam to purified water.