Every living being needs water to survive. Over 70% of adult human body is made out of water.
Water in your home typically comes from a public source such as ground water (a well), or surface water (a river). In order to know the quality of your water you must know where it comes from. Over 52% of americans depend on ground water as source of drinking water.
U.S. Environmental Protection Agency provides information about sources and quality of your local drinking water: EPA Local Drinking Water Information.
Although claims are made that the United States has one of the safest water supplies in the world, national statistics is often obscure and too broad. For instance, statistics will not tell you specifically about the quality and safety of the water coming out of your tap. That's because drinking water quality varies from place to place, depending on the condition of the source water from which it is drawn and the treatment it receives.
You can never be 100% sure what comes down the water pipes into your home. Water in your tap is often contaminated with bacteria, chlorine and other pollutants from chemical and pharmaceutical industry. If you want to feel protected from accidents - that do happen quite often - you best choice is to install home water filtration system.