Drinking Water Rules

toddler drinking from fountain

Congress authorizes the United States Environmental Protection Agency (EPA) to establish drinking water standards to protect the nation's drinking water supplies against contaminants that are likely to be present in the water. These standards are called Maximum Contaminant Levels (MCL) and Action Levels (AL).

How these standards are enforced:

  • The Arizona Department of Environmental Quality (ADEQ) enforces the standards in this state through the ADEQ Primacy agreement, where EPA grants ADEQ the rights and responsibilities to oversee the drinking water rules and programs in effect.
  • Local governments and private water suppliers have direct responsibility for the quality of the water that flows to your tap. Tucson Water tests and treats the water, maintains the distribution systems that deliver water, and reports on water quality to the state.
  • ADEQ provides technical assistance to water suppliers and can take legal action against systems that fail to provide water that meets these standards.
  • Tucson Water's Environmental and Regulatory Compliance Section (ERCS) oversees the Drinking Water Regulatory Program.

Regulated Contaminants

A list of the more than 89 regulated drinking water contaminants Tucson Water is required to monitor for and their levels to comply with several drinking water rules.

Sources of Contaminants

The Drinking Water Table lists sources of contaminants in drinking water. It was derived from the EPA's Drinking Water Contaminants  web page.​