Disinfection is considered by many to be one of the most important scientific advances of the 20 th century. Adding small amounts of lime achieves a slightly alkaline chemical balance, which prevents the water from corroding distribution pipes and equipment as well as consumers' plumbing. In addition to increasing the longevity of the distribution system, the lime reduces the leaching of substances such as lead from plumbing. Powdered activated carbon is occasionally used for taste and odor control. After the water has completed its path through the treatment process, it is referred to as finished or potable water.
Most people simply call it drinking water.
Another site which provides information on treatment processes and interesting links is the Environmental Protection Agency's How is Drinking Water Treated web site.