Water distillers use electricity to heat tap water to boiling point. Generally the Impurities are left in the container and the purified contents go back to a clean container. They need a higher level of efficiency and cannot give immediate supply, because the boiling process must be over before water is present. There are a number of reports in http://www.water-filters-purifiers-softeners.com/ that distilled water is not fit for health because it takes away nutrients from the body, being the most 'unnatural' of water.
Ionized Water Filters
These are generally filtered using an acid and an alkaline. They run between the positive and the negative ends of the electrodes and get the charged and acidic water. They are formed using 70% alkaline water and 30% Acid water. Alkaline and Acidic waters have unusual properties and benefits, but anyway their respective uses could not be more different.
Back flush Water Filters
They are costlier compared to charcoal filter units, but justify this by their claims of longevity. They are highly durable and efficient.