The Safe Drinking Water Act, passed in 1974, required the Environmental Protection Agency (EPA) to develop guidelines for the treatment and monitoring of public water systems. In 1986, amendments to the act accelerated the regulation of contaminants, banning the future use of lead pipe, and requiring surface water from most sources to be filtered and disinfected. The amendments also have provisions for greater groundwater protection. Despite the improvement these regulations represent, only public and private systems that serve a minimum of 25 people at least 60 days a year are covered by them. Millions obtain their drinking water from privately owned wells that are not covered under the act.

Drinking water comes from two primary sources: surface water and groundwater. Surface water comes from a river or lake, and groundwater, which is pumped from underground sources, generally needs less treatment. Contaminants can originate either from the water source or from...