The water supply in the United States is considered to be safer than in most parts of the world. Only 15 million Americans are not receiving treated water from their public water system.
For these 15 million people who rely on private well water, their sole protection against dangerous contaminants, which may be odorless and colorless, is a quality water filter. Most rural supplies may be safe because some groundwater is filtered naturally. However, shallow wells or area pollution sources may compromise its integrity. Contamination can even come from the ground itself, if fluoride deposits or arsenic is nearby.
Even those drinking supposedly safe public water should consider a water filter in their home, as contaminants can survive in heavily treated water as well.