Yes, tap water is closely regulated to ensure that it is "potable" i.e. safe to drink, at the point of use, usually your kitchen tap. However, the chlorine which is used to sterilise our drinking water has an unpleasant aroma and taste. Also, it is desirable for both taste and health reasons to remove impurities which are present in tap water at legally accepted levels or which are introduced via household plumbing, e.g. sediment, copper or lead.