The present invention relates to a method for treating tap water, comprising the steps of exposing running tap water to UV radiation with UV generating means capable of exposing the water to UV light for creating radicals, which radicals treat the water. The invention is characterised in the introduction of carbon dioxide bubbles upstream said UV generating means. The carbon dioxide bubbles create a scattering of said UV light for enhancing the treatment, and they also carbonate the water for drinking purposes.
