Cleaning windows with a purified water leaves your windows clean and shiny without any streaks or stains. Pure water, also known as purified water, is water from a source that has removed all impurities. Distilled water is the most common form of pure water. Pure water can be purified by carbon filtration, micro-porous filtration and ultraviolet oxidation. Some places use a combination of purification processes. Deionized water is a cheaper imitation of distilled water. This type of pure water has been stripped of all mineral ions, such as calcium, copper and iron. The deionization process is a physical process that uses ion exchange resins that remove the mineral salts from the water. Deionization is an inexpensive way to create a form of pure water. And this the water we use.