The Environmental Protection Agency has not done enough to ensure that all Americans have clean drinking water, according to a federal report. The majority of the water systems that have seriously violated drinking water rules in 2011 had not come back into compliance by last year, the Inspector General finds.

Just three of the 12 water utilities that received violations in 2011 had resolved their problems by April 2015. The 12 systems serve almost 5,000 people, according to the report.

"Since the 12 Arizona systems were not vetted through our reporting process, we recommend you to contact ADEQ or EPA Region 9 for further information on the status of serious violators within the state," spokesman Jeffrey Lagda said in an email.

The systems examined by the report serve around 3,300 or fewer customers, and are less likely than larger systems to have the capacity to monitor for contaminants or fix problems. Challenges for these utilities are to adapt to new standards, upgrading infrastructure, protecting source water and fighting budgetary constraints, according to the report.

The EPA said a work group is determining the best practices to bring small water providers into compliance. The agency said that it has made progress in finding non-compliance problems that pose serious health risks and ensuring violations are fixed in a timely fashion. The OIG report says that the agency's efforts have "shown some improvement over time."

By Premji